10. Allie Reynolds, 1947-54: Reynolds was acquired from Cleveland for Joe Gordon following a poor 1946 season for both (Gordon batted .210/.308/.338 with a 79 OPS+; Reynolds was 11-15 with a 3.88 ERA, 85 ERA+). In his first six seasons with the Yankees, Reynolds averaged 36 games, 29 starts, 233 innings pitched, an 18-8 record, with a cumulative 3.29 ERA and 117 ERA+. He led the league in ERA once, shutouts twice and strikeouts once. In 1953-54, he made more relief appearances than starts, going a combined 26-11 in 77 games (33 starts) with a 3.36 ERA and 106 ERA+. He hurt his back in a bus accident in 1954 and retired after the season. In eight seasons with the Yankees, Reynolds was 131-60 with a 3.30 ERA and 115 ERA+ in 1700 IP. In six World Series (all wins), 7-2 with a 2.79 ERA and five saves in nine starts and six relief appearances. He made five all-star teams and threw two no-hitters in 1951. He ranks tenth in team history in wins, ninth in winning percentage (.686) and fifth in shutouts (27).
9. Andy Pettitte, 1995-03, 2007-10, 2012-13: You may have heard of this guy. After a solid rookie season in 1995, he averaged 31 starts, 202 IP and a 17-9 record over the next eight seasons, with a cumulative 3.92 ERA and 117 ERA+. After a three year detour in Houston, he came back to the Bronx for four more seasons of solid production (54-34, 4.08 ERA, 110 ERA+) before retiring after the 2010 season. He came back last year and was great in 75.1 IP, before struggling this year. In 425 starts and 2715 IP across 15 seasons with the Yankees, he's 215-123 with a 3.88 ERA and 114 ERA+. He's made 40 postseason starts for the Yankees, pitching 251.1 innings with an 18-10 record and 3.76 ERA. I wrote a whole post about where he could end up on the Yankees' all-time pitching leader boards here.
8. Waite Hoyt, 1921-1930: The Yankees acquired him from the Red Sox prior to the 1921 season following two mediocre years in Boston (3.85 ERA and 87 ERA+ in 226 total IP. In his first eight seasons with the Yankees, he averaged 41 games, 30 starts, 253 IP and an 18-11 record with a cumulative 3.38 ERA a 119 ERA+. After a below average year in 1929, the Yankees traded him to Detroit two starts into the 1930 season. He pitched eight more seasons, going 72-74 with a 3.76 ERA and 110 ERA+ for the Tigers, Athletics, Dodgers and Pirates. As a Yankee, he pitched in 365 games, made 276 starts, and was 157-98 with a 3.48 ERA and 115 ERA+ in 2272.1 IP. In six World Series with the Yankees (three wins), he went 6-4 with a 1.83 ERA in 12 games and 83.2 IP. Hoyt ranks ninth in team history in wins, eighth in IP, seventh in starts and sixth in complete games (156). He won 237 games in his career and was elected to the Hall of Fame by the Veteran's Committee in 1969.
7. Mel Stottlemyre, 1964-74: Stottlemyre had a 1.42 ERA in 152 Triple-A innings when the Yankees called him up in 1964. He went 9-3 with a 2.06 ERA (177 ERA+) in 12 starts the rest of the season, helping the Yankees to their fifth straight pennant. He made three starts in their World Series loss to the Cardinals, going 1-1 with a 3.15 ERA in 20 IP. He never returned to the postseason, destined to toil during the down years following the end of a 40-year dynasty. From 1964-73, he averaged 34 starts, 255 IP, a 16-13 record and had a cumulative 2.94 ERA and 112 ERA+. He tore his rotator cuff after 113 league-average innings in 1974, and was done as a player. He spent 21 seasons as the pitching coach for the Mets, Astros, Yankees, and Mariners, winning five World Series in that capacity. Stottlemyre made 356 career starts, and was 164-139 with a 2.97 ERA and 112 ERA+ in 2661.1 IP. He ranks seventh in team history in wins, fourth in IP, seventh in strikeouts (1257), fourth in starts, eighth in complete games (152) and second in shutouts (40).
6. Eddie Lopat, 1948-55: Acquired from the White Sox after two straight excellent seasons, he hit the ground running for the Yankees. In his first six seasons, he averaged 28 starts, 207 IP and a 16-8 record with a cumulative 3.10 ERA and 127 ERA+. Despite a 12-4 record in 170 IP in 1954, his 3.55 ERA was slightly below average (98 ERA+). Lopat was 4-8 with a 3.74 ERA (101 ERA+) though 12 stats in 1955 when the Yankees traded the 37-year-old to Baltimore, and he retired at the end of the season. He made 202 starts as a Yankee, and was 113-59 with a 3.19 ERA and 121 ERA+ in 1497.1 IP. Lopat made seven World Series starts for the Yankee dynasty that won five straight series from 1948-52, going 4-1 with a 2.60 ERA in 52 IP.
5. Herb Pennock, 1923-33: Pennock pitched infrequently and inconsistently for the A's and Red Sox from 1912-17 (fun dead ball era stat: his 2.79 ERA in 1914 resulted in a below-average 94 ERA+). He spent 1918 in the Navy during World War I before rejoining the Red Sox in 1919. Following four up and down seasons, the Red Sox traded him to the Yankees prior to the 1923 season, and he promptly went on a six-season tear. From 1923-28 Pennock averaged 37 games, 29 starts, 248 IP and a 19-10 record to go with a cumulative 3.03 ERA and 132 ERA+. He won 20 games twice, 19 twice more, and had third and fourth place finishes in the MVP voting. Then, just like that, he was pretty much done as an effective pitcher, even though he spent five more seasons with the Yankees. From 1929-32 he averaged 24 games, 19 starts and 143 IP, putting up a 4.61 ERA and 88 ERA+. All told, Pennock pitched 346 games for the Yankees, making 268 starts, going 162-90 with a 3.54 ERA and 114 ERA+ in 2203.1 IP. He won 241 total major league games, and was 5-0 with a 1.95 ERA in five World Series (one with the A's, four with the Yankees). Pennock ranks eighth in team history in wins, ninth in IP, ninth in starts and fourth in complete games (164). He was elected to the Hall of Fame by the Baseball Writers' Association of America in 1948.
4. Ron Guidry, 1975-88: Guidry was the Yankees' third round pick in the 1971 draft. In his first three minor league seasons, he put up a 3.15 ERA in 36 starts, with 7.2 H/9, 0.3 HR/9 and 9.2 K/9. The problem was the 6.2 BB/9. He spent the next three minor league seasons (1974-76) in the bullpen, making eight starts and 93 relief appearances, and the results were pretty much the same: a 3.42 ERA, 7.1 H/9, 0.3 HR/9, 10.3 K/9 and 5.2 BB/9. He made one start and nine relief appearances for the Yankees in 1975 and seven more relief appearances in 1976. Guidry made the big league bullpen out of spring training in 1977, and six of his first seven appearances were in relief. He moved into the rotation in mid-May, and the rest is history (I'm glad the Yankees don't jerk guys around between the bullpen and the rotation anymore). From 1977-83 Guidry averaged 32 games, 29 starts, 220 IP and a 17-7 record with a cumulative 2.96 ERA, 131 ERA+ and 2.6 BB/9. He had a tough year in 1984 (4.51 ERA and 84 ERA+), bounced back to finish second in the American League Cy Young voting in 1985 (22-6, 3.27 ERA, 123 ERA+), then slipped to a 3.98 ERA and 103 ERA+ in 192.1 IP in 1986. A contract dispute and injuries limited him to 117.2 IP in 1987, but his 3.67 ERA was good for a 121 ERA+ in the "rabbit ball" season. Surgery limited him to 56 IP in 1988, and he retired after seven minor league rehab starts in 1989. Guidry finished his career with a 170-91 record in 323 starts, a 3.29 ERA and 119 ERA+ in 2392 IP. In 10 postseason starts, he was 5-2 with a 3.02 ERA, including 3-1 with a 1.69 ERA in four World Series starts. Guidry ranks fifth in team history in wins, seventh in IP, third in strikeouts (1778), fifth in starts and sixth in shutouts (26).
3. Red Ruffing, 1930-42 and 1945-46: The Red Sox traded Ruffing to the Yankees early in the 1930 season after five full seasons of mostly poor results: a 39-96 record, 4.61 ERA, 92 ERA+ and league-leading totals of 25 and 22 losses the previous two seasons. He was okay for the Yankees the remainder of the season, going 15-5 with a 4.14 ERA and 105 ERA+ in 197.2 IP. In 1931 Ruffing looked like the guy the Red Sox traded: a 4.41 ERA and 91 ERA+ in 237 IP. I don't know what changed between the 1931 and 1932 seasons, but from 1932-42 he was a different pitcher. Over those next 11 seasons, he averaged 31 games, 29 starts, 21 complete games, 235 IP and a 17-9 record with a 3.39 ERA and 123 ERA+. He won 20 games four straight seasons, led the league in wins once, shutouts once, strikeouts once and K/9 twice. He missed 1943 and 1944 due to World War II, but came back in the second half of 1945 and went 7-3 with a 2.89 ERA at the age of 40. He could only give the Yankees eight starts in 1946, although he went 5-1 with a 1.77 ERA. The Yankees released him after the season, and he made nine awful starts with the White Sox in 1947 (6.11 ERA in 53 IP). As a Yankee, he made 391 starts and went 231-124 with a 3.47 ERA and 119 ERA+ in 3168.2 IP. Ruffing also pitched in seven World Series (of which the Yankees won six), going 7-2 with a 2.63 ERA in 10 starts. He ranks second in team history in wins (five behind Ford), second in IP (1.2 behind Ford), third in starts (47 behind Ford), first in complete games (261) and second in shutouts (five behind Ford with 40). He really came within his two war seasons of being atop the Yankees' all-time leaders in half a dozen categories, but wasn't quite as good as Ford: a 119 ERA+ to Ford's 133, and 3.47 ERA to Ford's 2.75. If you like WAR for comparing career value, Ford tops him 53.9 to 46.8. He does top Ford by about two-third of an inning per start, which counts for something. None of this is to disparage Ruffing, just to illustrate how significant he is in team history despite the fact that he's largely forgotten today. He was elected to the Hall of Fame by the BBWAA in 1967.
2. Lefty Gomez, 1930-42: Gomez pitched 60 unremarkable innings for the Yankees in 1930, was awesome in 1931 (21-9, 2.67 ERA, 150 ERA+ in 243 IP) and mediocre in 1932 when his 24-7 record belied his 4.21 ERA and 97 ERA+. Over the next seven seasons, from 1933-39, he averaged 31 starts, 238 IP and a 17-10 record with a cumulative 3.08 ERA and 139 ERA+. He led the AL in wins twice, ERA twice, complete games once, shutouts three times, IP once, strikeouts three times, and K/9 twice (how times have changed: both years he led the league with 6.3 K/9). An arm injury limited him to 27.1 IP in 1940, but he bounced back to go 15-5 with a 3.74 ERA and 106 ERA+ in 156.1 IP in 1941. Injuries limited him to 80 ineffective innings in 1942, and he made one start for the Senators in 1943 before calling it a career. In 368 games, 319 starts and 2503 IP for the Yankees, he posted a 189-102 record with a 3.34 ERA and 125 ERA+. He pitched in five World Series (all wins), going 6-0 with a 2.86 ERA in seven starts. Gomez ranks fourth in team history in wins, fifth in IP, fifth in strikeouts (1468), sixth in starts, second in complete games (173) and fourth in shutouts (28). He was elected to the Hall of Fame by the Veteran's Committee in 1972. I went back and forth between Gomez and Ruffing several times, but I ended up going with Gomez. Even though Ruffing threw almost 700 more seasons and accumulated some more counting stats, Gomez's peak was a little bit better, and he was a little more dominant.
1. Whitey Ford, 1950 and 1953-67: Who else? The Yankees called him up at the end of June 1950, just as the war that would cost him the next two seasons was breaking out on the Korean Peninsula. In 12 starts and eight relief appearances, Ford went 9-1 with a 2.81 ERA (153 ERA+). He returned for the 1953 season, and over the next 12 seasons averaged 34 games, 31 starts, 225 IP and a 17-7 record with a cumulative 2.72 ERA and 134 ERA+. Casey Stengel often saved him for better opponents, but starting in 1961 Ralph Houk let him pitch every fourth game. Did it matter? In eight seasons under Stengel, Ford averaged 28 starts, four relief appearances, 205 IP, a 2.70 ERA and 136 ERA+. In the first five post-Stengel seasons (before he started breaking down), he averaged 37 starts, one relief appearance, 260 IP, a 2.85 ERA and 127 ERA+. From that quick look, it appears the effect was on the quantity, not the quality of his statistics. It was also the quantity of innings, not the quality, that led to Ford's retirement after the 1967 season. In 1966 he put up a 2.47 ERA and 135 ERA+ but was limited to 73 IP. In 1967 he posted a 1.64 ERA and 192 ERA+ but was limited to only 44 IP. In 16 seasons, he totaled 438 starts, 498 total appearances, and was 236-106 in 3170.1 IP with 156 complete games, 45 shutouts, a 2.75 ERA and a 133 ERA+. He led the league in wins and winning percentage three times each; ERA, shutouts and IP twice each; and complete games and ERA+ once each. Ford played in 11 World Series (the Yankees won six), and went 10-8 with a 2.71 ERA in 22 starts. Ford ranks first in team history in wins, eighth in winning percentage, ninth in H/9, first in IP, first in starts, sixth in complete games, and first in shutouts. He was inducted into the Hall of Fame by the BBWAA in 1974.