The current Yankees' roster gets a lot of flack for being old. Which, to be fair, is somewhat true. The Yankees have a couple of key players that are far closer to the end of their career than the beginning. However, none of the current Yankees are as old as Johnny Cooney was when he played for the team.
Cooney made his major league debut with the Boston Braves in 1921 at just 20 years old. He didn't become a real regular in the majors until 1924 when he made 19 starts for the Braves. He had a good season in 1925, but started to trail off after that. Cooney didn't pitch at all in the 1927 season and would pitch just 141.2 innings over the next three seasons.
In Hank Greenberg's autobiography, the Hall of Famer wrote about a conversation he had with Cooney before a spring training game in 1930:
Our manager, Buck Harris, started me in the first exhibition game, against the Boston Braves and Johnny Cooney. Before the game started Cooney took me aside and said "Kid, I'm gonna give you one you can hit." I don't know why, maybe he heard about my troubles. He was just as good as his promise, and I hit that fat pitch over the fence.
He might not have needed to grove that pitch, considering he threw just seven innings with a 18.00 ERA in 1930. He never pitched again after that season.
Cooney then disappeared from the majors for five seasons. After playing a couple years in the minors, he reappeared with the Brooklyn Dodgers in 1935. Only now, he was an outfielder. He had been a decent hitter during his pitching career, so it maybe it wasn't the craziest thing to happen.
Cooney would play for another ten seasons as a position player. He fared much better as a position player, receiving MVP votes in three seasons. Considering that the end of Cooney's career overlapped with World War II, that probably allowed him to extend his career longer than he otherwise would have.
After three seasons as a position player with the Dodgers, Cooney returned to the Braves in 1938. After several more seasons in Boston, he went back to the Dodgers in 1943. He continued playing into his age 43 season with the Dodgers in 1944. He played just seven games for the Dodgers in 1944 before being released on June 14.
Three days later, the Yankees signed the 43-year old. The 1944 season was the same one in which the Yankees signed a 41-year-old Paul Waner. For all the flack the current Yankees get for being old, at least they aren't that old.
Cooney played ten games with the Yankees in 1944 before being released on August 4th. He hit just .125/.222/.125 in his time with the Yankees.
Cooney played his final major league game on July 30, 1944. That one final appearance was just enough to make him the oldest Yankee position player ever. Enos Slaughter is second, having made his last appearance as a Yankee when he was 43 years and 129 days old. Cooney's appearance came when he was 43 years and 134 days old. By just five days, Johnny Cooney is the oldest New York Yankees' position player ever.
While not many players still play to 43 today, there's always a chance someone will break Cooney's record. There are no likely candidates right now, though. It make take a weird set of circumstances to surpass Cooney's record which came because of a weird set of circumstances.
All data courtesy of the Baseball-Reference Play Index