So De La Rosa made two last relief stints for the Dodgers' organization after the trade -- the last of which was for Double-A Chattanooga on Aug. 31. Then he had to sit around and do nothing for the rest of the season.
Obviously the Red Sox didn't want their future property risking injury for another team.
"For me, I was sick," said De La Rosa, who is in Boston for the Red Sox's Rookie Development Camp. "I was not allowed to be around and play. I was there for a few weeks. At Double-A, I couldn't do nothing. Just run, condition, work out. That was sad for me. I wanted to go home. I talked to my agent and said, 'I want to go home, because this is bad. Everybody is playing and I'm not playing.' So I needed to focus on other things. It was a bad experience for me."
But the day after the regular season ended, De La Rosa was officially moved to the Red Sox, bringing him great joy.
It was not lost on him the magnitude of players he was traded for.
"I was like, 'Wow, that made me happy. OK, Boston thinks good things about me.' To go there and try to win a championship, that would be a good feeling for me," said De La Rosa. "My reaction when they told me was, 'OK, probably Boston needed me more than [the Dodgers].'"
That much is probably true.
The Red Sox badly need some young studs to put in their rotation, and while De La Rosa might not be quite there yet, it might not be long before he takes up permanent residence at Fenway Park.
The coming season is for De La Rosa to prove that he is healthy again, after undergoing Tommy John surgery in August 2011.
"I'm still working my way back," De La Rosa said. "I feel back, but I'm still working. When I go back to the game, I'm not thinking it's hurt. I'm not afraid. It's just pitching."
Before the injury, De La Rosa was hyped as a potential star -- one of the best pitching prospects not just for the Dodgers, but in all of baseball.
"He looks good," said director of player development Ben Crockett. "He's definitely been ready with his throwing program. You can tell he's been working hard on the arm strength. He told us he's been throwing for quite a while, and it shows -- really quick arm, ball is jumping out. He's aggressive and confident with that throwing program. He's mixing in some of his offspeed [pitches] and he looks like he's ready to compete."
De La Rosa will be 24 in March, and he still has ample time to reach that promise. He has a fastball that travels in the mid-to-upper 90s and a changeup many scouts have graded as "plus."
While De La Rosa gets ready for his first Spring Training camp with the Red Sox, he has tasted Major League life before. In 2011, the righty pitched in 13 games for the Dodgers, 10 of them starts, going 4-5 with a 3.71 ERA.
De La Rosa had just made it back to the Majors last season, getting in one relief appearance just before the trade.
De La Rosa is a starter at heart -- and that is almost assuredly where he will wind up long term -- but he will seize any opportunity that might be there during Spring Training.
"Yeah, right now, I'm in preparation to take any position that's open -- reliever, starter, closer, I'm going to take it," De La Rosa said.
It will comfort Red Sox fans to know that De La Rosa, a native of the Dominican Republic, has some fairly accomplished mentors. Through his grandmother, De La Rosa has known Ramon and Pedro Martinez since he was a kid.
Ramon is the one who De La Rosa has had more interaction with throughout the years. But Pedro, the Red Sox icon and near certain future Hall of Famer, is the one who taught him his current changeup.
"I don't watch a lot of baseball," De La Rosa said, "but all the time Pedro pitched, I watched all the time. I had to watch what he did. I want to be like him every time. When I grew up, I watched him all the time, and I was him when I played video games and everything."