Wielding an improved changeup that tipped the scales in his favor, Hughes grabbed the job over competitors Joba Chamberlain, Alfredo Aceves and Sergio Mitre in what began as a five-man race. Chad Gaudin, the final candidate, was released on Thursday.
"We evaluated the whole spring," Girardi said. "I'm very excited with the improvement in [Hughes'] changeup. To me, that made a big difference in who he is. Our decision is for him to be the fifth starter, and all the other guys are competing to be in the bullpen."
The 23-year-old Hughes has made four spring appearances, striking out 10 and walking only two while allowing 12 hits in 13 innings. He will be bumped up to pitch against the Phillies on short rest Friday, which aligns him for the fifth spot in New York's rotation.
"What I set out to do this spring was win that job," Hughes said. "I felt like I did everything they asked me to do. They felt like I was the right guy for the spot. It was something that I really wanted.
"I feel like I'm ready for the challenge and ready for the season that lies ahead. I'm just looking to go out and put together as many quality starts as I can and give our guys a chance to win every day. That's really all I can ask from myself."
In some circles, Chamberlain had been viewed as a leading candidate heading into the spring, as the Yankees had spent the better part of the previous three seasons building up his innings count so that he could pitch without limitations in 2010.
But Chamberlain floundered early and, with Hughes strengthening his grip on the organization's attention, never seemed to win back that lost time.
"You go with the flow," Chamberlain said. "That's what I've done."
Chamberlain has yielded 12 runs on 10 hits in 6 2/3 innings for a bloated ERA of 16.20. He will be given a chance to win the setup role in the bullpen, the job he held -- and excelled in -- when he took New York by storm upon reaching the Majors in late 2007.
But Girardi said that it is not a sure assignment, mentioning that he also could consider Damaso Marte, Chan Ho Park and Dave Robertson to record important outs in the late innings.
"We've got to see how he does here in the bullpen," Girardi said. "There's no guarantees that if you were in that five-man race, you're automatically going to the bullpen. In a sense, you've got to prove yourself. But we do like the way the guys are throwing the ball."
Girardi said that he believes Chamberlain could either start or relieve at the Major League level, but that Hughes is ahead at this point in time. Girardi said that he did not feel that building Chamberlain up for the opportunity was a wasted experiment.
"There were things that we wanted to look at -- we won a World Series and he was really extremely helpful when Chien-Ming Wang went down," Girardi said. "He stepped up and was our fourth starter. If you look at his first four months, he pitched pretty well; he really did. So I don't think it was a waste."
Girardi said that he informed both Chamberlain and Hughes of the decision before leaving George M. Steinbrenner Field on Thursday for Sarasota, where the Yankees played a Grapefruit League exhibition against the Orioles.
The two remaining candidates, Aceves and Mitre, were slated to pitch in the game as well. Both can think about bids for relief jobs. Chamberlain will make a relief appearance on Saturday against the Tigers, pitching one inning. He congratulated Hughes on winning the job.
"We're all teammates again," Hughes said. "I think we all trust in the front office and the coaching staff to make the right decisions. We just get paid to go out and throw the ball. There's no bitterness or anything like that.
"We're all pulling for the same goal, to do what we did last year. The roles might be switched and there might be some different guys on the team, but we're pulling for each other."
While Hughes will be subject to innings restrictions similar to the ones Chamberlain has handled, the Yankees believe that they will be more manageable.
Because of more Minor League work, Hughes' innings limit will be slightly higher than Chamberlain's 157 1/3 frames in 2009 -- perhaps about 170 -- and the Yankees plan on skipping Hughes occasionally, as is customary with a fifth starter.
"They said it will be something they look at," Hughes said. "I don't foresee it being a huge issue. I don't think anyone has got the exact formula for it, how to keep a guy healthy. I'm not going to be worrying about it."
Hughes was a first-round Draft pick in 2004, arriving in the big leagues early in '07. He looked like a star on the fast track when he pitched 6 1/3 no-hit innings against Texas in his second Major League start, but a hamstring injury sent him to the disabled list.
He worked in only eight Major League games and the same number of Minor League games in 2008. Hughes opened last season with Triple-A Scranton/Wilkes-Barre, was promoted in late April and went 3-2 in seven starts.
On June 8, he made his first relief appearance of the season, and he went on to claim the eighth-inning role, pitching in front of closer Mariano Rivera.
"He was really tested last year mentally," Girardi said. "You get in those jams in the course of a game, and you've got to turn into that tough mentality to get out. I think he learned a lot last year."
Bryan Hoch is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.