"I was a little frustrated at first, because I want to be a starter. But I understood," Warren said before Tuesday's matchup with the Angels at Angel Stadium. "They sat down and talked to me about it, explained it. I understood where they were coming from. I told them I'm not going to be unhappy in the bullpen."
Warren, 27, was 5-5 with a 3.59 ERA this season, and said that Girardi told him on Monday that he would not be making Wednesday's start against the Angels, as was initially announced. Nathan Eovaldi will make that start instead, and Warren is available to pitch in relief immediately.
"We've looked at a lot of different things, innings being one," Girardi said. "He's done it in the bullpen and been really successful. He's really the only one in the rotation that's done that. It's a tough decision because he's pitched so well, but it's what we need to do."
Warren should be able to assist an area of the team that was viewed as a strength coming into the year, but has taken some hits recently, most notably the loss of closer Andrew Miller to injury. Girardi said that he could use Warren anywhere from the sixth inning to the ninth to take some of the strain off Dellin Betances, Justin Wilson and Chasen Shreve.
"Those guys have worked pretty hard here lately and they have a ton of games already, and it's only halfway," Warren said. "If I can take some of the workload off of them, that's kind of the goal. Give them another right-hander to help out."
Part of the Yankees' thinking was that Warren had already thrown 82 2/3 innings, his most in a Major League season and his highest total since tossing 152 2/3 frames at Triple-A in 2012. The Yanks say they do not have an innings limit on Warren, but he was on pace to exceed 180 innings, which wasn't going to fly.
"It's still a little frustrating," Warren said. "I feel like I've gotten into a little bit of a groove. I understand where they're coming from and that they mean well by it."
The decision means that the Yankees' rotation will be comprised of Masahiro Tanaka, Michael Pineda, Eovaldi, Ivan Nova and CC Sabathia, who fell to 3-8 with a 5.59 ERA after losing to the Angels on Monday.
Girardi said that the Yankees never considered removing Sabathia from the rotation; Sabathia is owed $23 million this season and $25 million next, ensuring that he will have opportunities to work out his issues.
"That's what we've counted on him to do," Girardi said. "He threw a decent game last night and he's had some good games. I know the ERA is in the fives, but could CC have six, seven wins? I think so. And maybe we're not talking about it as much if in some of these games he had some run support."
Girardi said that it is possible the Yankees could call on Warren again as a starter this season. Warren said that he still sees himself in that role, and hopes that the Yankees will give him the opportunity in the future.
"I really enjoyed the pitching aspect of being a starter this year, going through hitters two or three times, the mindset of pitching and thinking through the game," Warren said. "That's something I still consider myself as."