Adam Warren becoming a late-inning force out of the bullpen

Thanks to Mariano Rivera's retirement and David Robertson's current injury, the Yankees needed someone to step up in their bullpen; Adam Warren has done just that.

Once spring camp broke, the Yankees decided to take three pitchers who can start in David Phelps, Adam Warren, and Vidal Nuno to Houston and placed them in their bullpen. Given all three can start, it was unclear how exactly they'd be used and who would stand out among the three. Through a week-and-a-half, however, it is Warren who has separated himself from the rest.

When CC Sabathia struggled during the first two innings of the very first game against the Astros, Adam Warren was spotted in the bullpen warming up. This kind of made sense, because Warren was used as the team's traditional long-man last summer. He never entered the game, though, as Sabathia was able to settle down and hold the Astros to six runs through six innings. But, at the time, it figured Warren would, once again, settle in as the team's long-guy who pitched in mostly lower-leveraged spots as opposed to more pressure situations.

Two games later, though, on April 3, Warren was used in a pressure spot instead of a long-relief role. Ivan Nova walked his fifth batter of the evening and was only at 88 pitches, but Joe Girardi had seen enough. The manager went to Warren in a one-run game against Astros' shortstop Jonathan Villar and the right-hander got a quick three-pitch strikeout. After the Yankees tacked on an insurance run, Warren proceeded to pitch a nice and easy 1-2-3 seventh which included a strikeout and two weak ground outs.

Next up was the April 6 win against the Toronto Blue Jays. As you may recall, this was the game where CC allowed a lead-off homer to Melky Cabrera in the first and proceeded to cruise until the second out of the sixth inning. It was a 6-1 game with two out in the sixth, but some balls were hit hard and some other balls found holes and just like that it was 6-4. Instead of using a long-guy or whatever to soak up the final three innings of a five-run game, the Yankees had to go to someone they could trust in the late innings of a two-run game, and, once again, that was Warren. Facing the 8-9-1 batters, Warren was able to induce short flyballs to Moises Sierra and Jonathan Diaz before getting Cabrera to ground back to Warren for the third out. After just a couple of scoreless outings, Warren really seemed to earn Girardi's trust.

Warren's next outing was another pressure spot, this time coming during the team's home opener against the Baltimore Orioles. After Hiroki Kuroda, Matt Thornton, and David Phelps combined to keep the score at 4-2 through the seventh, Girardi went to Warren in a two-run game to pitch the eighth. Instead of pitching against the Astros' and Blue Jays' respective bottom of the lineups, Warren had to face the top of the Orioles' order. He first walked David Lough (whoops) to lead off the inning, thus Vidal Nuno began to warm up thereafter. Warren was able to get the next two batters, Nick Markakis and Adam Jones, to flyout, which set up last year's home run leader, Chris Davis, as the tying run. Instead of going to the lefty Nuno in that spot, Girardi stuck with his right-hander and Warren rewarded his manager with a big strikeout of Davis to keep the game at 4-2.

The Yankees have kept going to Warren in close, late-inning games and the right-hander has continued to flourish. During Wednesday's game against Baltimore, Warren came in a tie game in the eighth and was able to keep the game right where it was with two weak fly balls after allowing Adam Jones and Matt Wieters to reach base. In Friday's contest, the Yankees were trailing by two runs against the Red Sox, and Warren was able to hold the game at 4-2 through the top of the eighth. And, finally, in Saturday's game, Warren kept the Yankees ahead 6-4 with another easy 1-2-3 inning, which included strikeouts of Xander Bogaerts and Jonathan Herrera, with a weak ground out of A.J. Pierzynski in between.

Because he pitched in mostly mop-up situations last year, Adam Warren's average leverage index when entering a game was at just 0.56 (anything above 1.0 is higher pressure and anything below 1.0 is lower pressure). This figure, of course, was the lowest among Yankee relievers who made at least 30 relief appearances in 2013. Through his first six appearances of 2014, Warren's average leverage index has more than doubled, sitting at 1.34. That's a pretty big jump for a guy who pitched in mostly low-leveraged situations in 2013.

In terms of Warren's pitch usage and velocity in 2013 and through his first six appearances of 2014? Here are the numbers provided by Brooks Baseball:

I'm a little surprised that Warren's fastball velocity hasn't jumped much at all now that he's in more of a one-inning role as opposed to a long-man role, but maybe that's a small sample thing. What is different about the two sets of data, though, is the usage of his pitches. Warren has thrown his four-seamer, change, and slider more this season than he did in 2013. He still is throwing his curve about the same amount of time this year than he did last year, but it's clear his three go-to pitches are the four-seamer, slider, and change.

When the Yankees voluntarily decided to stay in-house to fill out the rest of their bullpen (Matt Thornton being the exception), we knew someone needed to step up. David Robertson replaced Rivera as closer and Shawn Kelley replaced Robertson as setup man, but we didn't really know who would replace Kelley as the seventh inning guy. Personally, I thought Warren would be one of the last guys who'd fill that role, but so far he has passed with flying colors, as shown by his 0.00 ERA and 1.88 FIP. Sure, there's a lot of season left to be played, and bullpens can change quite a bit as the season progresses, but Warren has done a great job in the late innings of close games for the Yankees.