Two-thirds of June is in the books, and it is officially Summer. The Yankees bullpen has largely looked the part of the dominant force that most expected this month, leading all bullpens in K/9, while sitting 2nd in BB/9, 2nd in K/BB, and 6th in fWAR. Despite this, the bullpen also sits dead last in ERA, with an ugly 5.47 mark .
Much of the blame for this has been laid at the feet of the non-No Runs DMC crew - but that isn't entirely fair. Dellin Betances sports a 5.00 ERA in June, having allowed runs in four of his nine appearances. Aroldis Chapman's ERA is a bit better, at 4.70; however, he has allowed runs in four of eight appearances (though, to be fair, one of those games involved an unearned run). Andrew Miller has held down the fort, though, with a tidy 2.00 ERA. In this case, however, two out of three isn't too good.
When two of the Yankees three bullpen aces are struggling, it becomes much more difficult to mask the shortcomings of the Kirby Yates's of the world (though, I'm not sure that anyone or anything could help Yates, who has a 15.19 ERA in June, having allowed 13 base-runners in 5.1 IP). On the season, Chapman and Betances have been mere mortals, with 3.18 and 3.24 ERAs, respectively. ERA may be something of a crude measure - but it is demonstrative of their inability to consistently 'shorten' the game. 168 relievers have thrown at least 20 IP ... and 73 of them have a better ERA than both Chapman and Betances.
If you prefer a more in-depth statistic, you could turn to WPA (win probability added), which aims to capture how much a player helped or harmed his team's win expectancy. Chapman currently sits 56th among relievers in WPA, while Betances is 62nd. Betances also has seven meltdowns thus far, which ties him for the second-worst in the league (and isn't too far from his career-worst of 10).
Heading into the 2016 season, the Yankees bullpen was supposed to be elite; some even felt that it would be the best ever, spearheaded by three men that were arguably among the top-five relievers in all of baseball. All the rotation would need to do was manage the game for five or six innings, and then turn it over to No Runs DMC. And yet as we approach the season's halfway mark, only Miller has been truly dominant.
The rotation as it stands is basically Sabathia, Tanaka, and pray for rain, and the overall 'good not great' nature of Betances and Chapman thus far simply isn't good enough for this team as constructed.
Coming full circle, there is cause to believe that Betances and Chapman will turn it around. In addition to their extraordinary résumés, both have excellent peripherals - Betances actually leads all relievers in K/9 (16.74) and fWAR (1.6), and sits second in FIP (1.29) and xFIP (1.16). It is here more so than anywhere else on the team that hope springs. Of course, the question then becomes whether or not it is too late...