Jonathan Holder is making the Yankees' bullpen even deeper

  If the Yankees harbored any doubts about Jonathan Holder appearing in high-pressure situations, perhaps those feelings have subsided for good. The 25-year-old right-hander, who entered the sixth inning of Monday night's game against the Washington Nationals with a 3-2 lead, escaped a first-and-third, nobody out jam by striking out Mark Reynolds and Daniel Murphy and getting Pedro Severino to fly out to shallow left field. It happened to be the turning point in the game, as the Yankees won the nightcap of the 1.5-game doubleheader in D.C. by a score of 4-2. "[Holder] continues to come up big for us. He's become a huge part of our bullpen," Yankees' manager Aaron Boone told the YES Network after the game. "Obviously, a huge spot there, a huge leverage spot. In a way, you're kind of just hoping to get out of there with a run and keep it tied. And Reynolds has a really good at-bat against him. He just kept making pitches. Just a big-time outing and our pen tonight, just a big-time performance by them." Holder has emerged as a reliable middleman out of the bullpen, which wasn't the case back in early April when he allowed a combined six hits and six runs in two consecutive outings. Those poor performances forced the Yankees to demote Holder to Triple-A Scranton/Wilkes-Barre for a brief two-week stint. But Holder has looked rejuvenated over the past two months. Since returning to the majors on April 21, he's struck out 21 hitters and allowed just seven hits and three runs in 20 innings (20 games).  "He went from a guy who, frankly, kind of barely made the team out of spring training, was sent down pretty early. And since he's come back, he's just earned more and more opportunities, earned bigger opportunities," Boone said. "The more guys we can have in the mix in those high-leverage spots, the more we can kind of protect each other. Just another terrific performance. So proud of what he continues to do."

Jonathan Holder cleans up Sonny Gray's mess. Men on the corners and Holder gets three outs. That was some performance. #Yankees pic.twitter.com/HO90Ch3QLy

— Tom Hanslin (@tomhanslin) June 19, 2018

Boone has noticed Holder's progress in throwing a slider, which essentially was an ineffective curveball early on in the year. That slider, along with Holder's changeup and fastball -- which has increased in velocity -- is keeping hitters off balance.  "The one thing he does great is pound the strike zone," Boone said about Holder. "But he's relied more on the slider, as opposed to the curveball earlier in the year and that's become a real weapon for him. The changeup's been a factor too against some lefties. So I think the slider and a little bump in velocity has been huge for him." Austin Romine, who was behind the plate on Monday night, hasn't noticed any stark differences in Holder's makeup. But he did mention that Holder has seemed more confident and relaxed on the mound.  "His conviction in his pitches. He's out there and he's positive, he's convicted in everything he's throwing," Romine told the YES Network. "When you've got that kind of conviction, that feeling like I'm attacking these guys, the pitches tend to work a little better, I guess. But I see a guy out there who's commanding the zone. "I just see a guy who's getting more comfortable at this level. And he's getting more innings under his belt and big innings for us. So, he's become one of our guys who we can go to, who we can trust, and he's been getting us out of a lot of big situations." Holder says his short return to the minors helped him regroup and adapt. He also understands that most young pitchers deal with growing pains and setbacks at the big league level. But Holder credits the opponent for his recent success, as hitters are exposing his strengths and weaknesses.  "Just letting the hitters tell me what's working and what's not working. I had to make a few adjustments, but that's what baseball's about," Holder told the YES Network. "Just trying to focus on those pitches and take it one pitch at a time... I'm trying to get out of it. "It's good to come in and have a little adrenaline run. I'm just trying to take it one pitch at a time and hand it over to the back end of the bullpen because they're pretty locked down." Holder hasn't been the Yankees' only dominant reliever. As a unit, the bullpen owns a 0.58 ERA in 46.2 innings this month, and in those innings, they've struck out 64 batters and allowed only 23 hits and three runs.   If you want to connect with Tom Hanslin, email him at thanslin@gmail.com or follow him on Twitter @tomhanslin.