PHILADELPHIA — In the offseason, New York Yankees manager Aaron Boone would tell anyone who’d listen about his belief in Brent Headrick. The left-hander pitched only 23 innings last season and spent more time in Scranton/Wilkes-Barre than New York, but there was no doubt in Boone’s mind: Headrick was going to pitch for the Yankees in 2026.That he has. Only one pitcher has appeared in more games this season than Headrick, who made his 52nd appearance on Friday night. And for the 44th time this year, he did not allow a run, a tally that leads MLB.Boone’s offseason premonition was right. Headrick has turned out to be a godsend for the Yankees.“I think he’s on the short list of guys that have been the best in the game that aren’t the full-time closer,” Boone said after the Yankees’ 1-0 win over the Philadelphia Phillies.Headrick has the third-highest fWAR among all relievers who are not full-time closers. The only non-closers who have been better than him are Atlanta Braves lefty Dylan Lee and San Diego Padres lefty Adrian Morejon, who is an intriguing trade candidate for the Yankees.On Friday, Headrick entered in the eighth inning in relief of Cam Schlittler with two on and one out. He allowed a single to load the bases for Philadelphia’s top of the order, then induced a lineout from Trea Turner and a Kyle Schwarber groundout to escape the jam.“You love to be in those situations,” Headrick said. “Any time my name’s called, I’m gonna give everything I have. I think it’s important to go out there with that same mentality every time. Guys on, guys not on, doesn’t matter.”Cam Schlittler struck out 12, the second-highest total in his 22 career starts. (Emilee Chinn / Getty Images)Headrick helped preserve a brilliant outing from Schlittler, who went 7 1/3 innings and struck out 12 batters in 99 pitches. Schlittler is continuing on a path to potentially becoming the American League Cy Young Award winner, as he lowered his ERA to 2.07 after his scoreless start against the Phillies.