The New York Yankees closed out the first half leading the American League East by 3.5 games, and 4.5 games over the Toronto Blue Jays. They currently trail the Jays by 4.5 games. There are plenty of reasons for that nine-game second half swing, for the most part those reasons have more to do with the Blue Jays winning 36 of 50 since the break than anything the Yankees have done. New York hasn't fallen apart in the second half as much as it has simply been run down by a red-hot Toronto team. Key injuries and offensive slumps haven't helped, but another area where the Yankees have seen a drop-off in the second half is in the bullpen.
One of the biggest strengths of the team in the first half, the Yankees posted 3.8 WAR out of the bullpen in the first half of the year, a mark behind only the Dodgers. They were doing this in key leverage situations as well, delivering the fourth best win probability added with a 4.12 WPA. The Yankees posted the seventh best ratio of shutdown to meltdown appearances, even with the early struggles from the likes of David Carpenter and Esmil Rogers dragging this stat down. The Yankees were also far and away the leaders in first half 'Clutch' from the bullpen, unsurprising given what Dellin Betances and Andrew Miller were doing in the highest leverage situations throughout the early months.
It wasn't just good sequencing though, as the peripherals backed the early success. The bullpen had a solid 3.47 FIP, seventh in the league, thanks to the second best relief crew strikeout rate of 10.10 K/9. The team has still been getting whiffs in the second half, but the K-rate has fallen slightly to 9.81. The walk rate has been high all year though, and has increased slightly in the second half to 3.69 BB/9. Slightly fewer strikeouts, slightly more walks, but the long ball is what has really been hurting the Yankee relievers in the second half, going from 0.83 to 1.27 HR/9. This leads to a post-break FIP of 4.11, putting them 21st among major league teams. Not a great number from a team that is meant to have one of the stronger bullpens in baseball.
They've been particularly disappointing over the last month. They are 18th in relief WAR over the last 30 days, and ninth in WPA, even without including the bullpen struggles in yesterday's double-header. Walks continue to hurt the team, with the fifth highest BB/9 rate in the league. Even Betances has not been exempted from the second half slump; fewer strikeouts and more walks has seen his FIP jump from a surreal 1.76 first half to a more average 3.41 second half. He's also only been worth 0.4 WAR since the break, which is a far cry from the 1.9 WAR he delivered from April through mid-July. Perhaps Betances has seen his control issues resurface due to fatigue from the workload he's had to endure over the last two seasons. Of course, it could also be some regression after such a dominant stretch in the early goings of his MLB career.
Meanwhile, Miller has remained a lock-down closer and Justin Wilson has been a consistent asset in bridging to the two late inning arms. The biggest drop-off, though, has come from Chasen Shreve. Arguably the third best reliever on the team in the first half, Shreve was a revelation in his second major league season. Having only thrown 12.1 innings in 15 appearences for the Braves last year, he seemed like a potential LOOGY when first brought over, but increasingly worked his way into higher leverage situations with a solid 0.5 WAR in the first half. Shreve has given that half-win back, though, since the break, and might have dropped below-replacement level with another tough appearance in the first game of yesterday's doubleheader. It's been an incredible jump in major league innings from 12.1 innings to over 50 this year, even though Shreve has had similar workloads in the minor leagues. Perhaps the higher stress and leverage of pitching, and pitching well, in big league situations has taken more out of him this year, or perhaps this is just a corrective slump from a pitcher who isn't quite as good as those first-half stats suggested. Either way, the loss of a highly productive Shreve has been a big part of the drop-off in the quality of the bridge to Betances and Miller, and while Adam Warren pitching well out of the bullpen helped mitigate some of that, he might now be needed back in the rotation with the injury to Nathan Eovaldi.
Warren, Wilson, Betances and Miller have been the only above-replacement pitchers in the Yankees bullpen over the second half of the year so far, and if Warren isn't a part of the bullpen the rest of the way then the Yankees will certainly need someone else to step up. Shreve has continued to get a steady stream of innings through his slump as Girardi might be hoping he works his way out of it and returns to being a valued late-inning arm again. Otherwise the Yankees might look for someone like Andrew Bailey to grow into a quality fourth reliever in the pen, or for some production out of the younger guys like Bryan Mitchell, Nick Goody, or Nick Rumbelow.
If the Yankees are to have a realistic shot of chasing down Toronto for the division, or to survive a potential bullpen duel in the one-game playoff, New York is going to need contributions from multiple relief pieces, and not solely depend on the strength of the Miller-Betances combo. The Yankees might well have a shot at advancing deep in the postseason if the bullpen can bounce back to resemble what it was in the first half and forget what they've looked like recently.