Over the course of the Yankees long run of success between the mid-1990s and the late 2000s, one man became a constant at the back of their bullpen: Mariano Rivera. With the greatest closer of all time shutting the door in the ninth, the bullpen became quite a dependable strength, a strength that continued with the signing of Rafael Soriano in 2011 and the development of new White Sox closer David Robertson. With the signing of Andrew Miller this offseason, plus the development of Dellin Betances and the trades for such interesting bullpen arms as David Carpenter and Chasen Shreve, the Yankees have acquired quite a bit of depth and skill in their major league pen.
That depth and skill carries over to the Triple-A pen. Jacob Lindgren, who posted a 1.23 ERA in 22 innings in Scranton/Wilkes-Barre this season, just got called up, but there's a lot more left where he came from. Jose Ramirez has finally made his first appearances this season, and should see some (potentially significant) time in the majors this season. Nick Rumbelow is another hard-throwing reliever waiting in Scranton who could also become a late-inning reliever and should also see some major league action this year. Danny Burawa is still just 26 and has a 1.50 ERA in 24 innings in Triple-A this season. Finally, Tyler Webb and Mark Montgomery are both in Triple-A as well, and both are just 24 with promising stuff and a decent amount of minor league success in their past. Montgomery might've actually been the top relief prospect in the system a year ago - and he certainly hasn't fallen off a cliff ability-wise - which just goes to show how loaded the Yankees are with near-ready relief talent waiting in Scranton.
Even in Double-A Trenton, the Yankees still have quite a bit of bullpen depth. Cesar Vargas continues to have success in the minors after converting from a starter into a reliever, and Kyle Haynes (part of the package the Yankees received for Chris Stewart) also is having a solid year after moving into the bullpen full-time upon joining the Yankees. Johnny Barbato is just 22 and sports a 1.52 ERA in Trenton - he profiles as a late-inning reliever, and while he did strain his UCL last year, making some fear that Tommy John was in his future, he has so far avoided surgery this year and had a very successful start to the season. Nick Goody is also currently in Trenton; he's only 23 and has an ERA under two early this season.
Lower in the system, the Yankees have some interesting arms in Tampa and Charleston, but none are sure things right now obviously. Also, many pitchers in the lower levels of the system are still determining if their ability and pitch repertoire might be better suited to being a member of the starting rotation or coming out of the bullpen. In the early going this season, though, 22-year old Yoel Espinal is off to a roaring start, managing a 0.42 ERA through 21.1 innings, and Rony Bautista and Cale Coshow have been practically unhittable at the end of games for the High-A Charleston RiverDogs. Tampa has seen Evan Rutckyj post a 2.28 ERA early in 2015, buoyed by his 32 strikeouts in 23.2 innings - unfortunately, Tampa has also witnessed closer Angel Rincon disappoint early on this season, as he's failed to get hitters to miss and has an ERA near five.
Relief depth is one of the main strengths of the Yankee system, and we'll begin reaping the benefits of this soon hopefully not that "the Strikeout Factory" has been promoted to the majors. Rumbelow or Burawa could follow, and even if they don't, the Yankees have enough talent and depth in their system that they should be able to have one of the better pens in the majors for the foreseeable future. With Andrew Miller and Dellin Betances locked up for the next couple years, all the talent coming up the pipelines means the Yankees bullpen will continue to be a major strength for the Bronx Bombers.