"The deal was never going to get done without Kelly's inclusion," said Padres general manager Jed Hoyer.
That's pretty heady stuff for the 21-year-old Kelly, a right-handed pitcher who had been the prized prospect of the Red Sox before he was included in the blockbuster deal that sent Gonzalez to Boston.
The enormity of it all -- the trade, a new organization -- was something that Kelly was still trying to process on Wednesday.
"It's a tremendous honor to be traded for [Gonzalez]," Kelly said. "It has been a crazy experience so far. I'm still trying to wrap my head around it."
Kelly, who was the Red Sox's first-round Draft pick in 2008, said that he's excited about joining the Padres' organization and is very eager to get to Arizona for the start of Spring Training in February.
"It's a little bittersweet -- the Red Sox treated me really well for the three years that I was there," Kelly said. "But I'm really excited for this next opportunity. I'm ready to start a new adventure."
Kelly, a former shortstop who made the move to the mound midway through the 2009 season, had a 5.31 ERA last season with Double-A Portland. It was his first full season pitching and he was the youngest pitcher in the league.
"Last year, I was throwing harder than ever before, but I had trouble with my command," Kelly said. "I want to be consistent more with my command, working on getting strike one."
Consider Kelly to be a work in progress. His fastball, according to Baseball America, sits at 90-94 mph and has topped out at 96. He also has a free-and-easy delivery that has been described as fluid and an advanced changeup, especially for someone with his pitching experience.
"Last year was a big learning year for me," Kelly said. "Figuring out what kind of pitcher I'm going to be and just keeping an eye on the process. Just being able to go through that experience is going to help."
There's a fair chance that Kelly could open the regular season at Double-A San Antonio, though if he has success, he could move fast. The Padres appear set in their starting rotation with the recent acquisition of Aaron Harang, and they are close to signing Dustin Moseley. Kelly could be ready for the Major Leagues by 2012 if he continues to improve.
That timeline might hold true for one of the other players in the Gonzalez trade -- first baseman Anthony Rizzo, who was a teammate of Kelly's in 2009 and '10.
"Watching him hit is a lot of fun," Kelly said.
The Padres also received a young outfielder, Reymond Fuentes in the trade, a player who fits what the team is looking for -- young, athletic, defensive-minded players with speed. The team will also receive a player to be named later.
But getting Kelly was the key to the deal and a reason why the Padres were able to part with a player in Gonzalez who they think very highly of.
"It's so hard to find affordable starting pitching in our market," Hoyer said. "Getting a guy that we feel can be in our rotation for a long time -- I think that he's an excellent fit for PETCO Park."