But general manager Theo Epstein sees something in Aceves that might separate him from some of his competitors.
"He's a versatile guy who can compete for a job in the bullpen but also provide valuable starting depth for us," Epstein said. "That's one area where we don't have tremendous depth with the composition of our roster and where we're at with the upper levels of our farm system. We really needed that -- someone who can start Major League games and compete in the American League East. His versatility and strike throwing and the fact that he's pitched well in this division stood out for us and made him a target."
Beyond the projected starting five, Tim Wakefield and Felix Doubront are two players who offer additional rotation depth. Aceves is now on that list as well.
Aceves pitched in just 10 games with the Yankees last year, but the Red Sox think he's regained his health.
"He threw two good [bullpen sessions] for us," Epstein said. "Obviously he had the back and hip issues last year then he broke his collar bone riding a bike this year. But he looked to be in really good shape. We'll assess him more thoroughly."
Another name added to the bullpen mix earlier this week was lefty Dennys Reyes, who signed a Minor League deal that includes an invite to Spring Training.
Hideki Okajima, Doubront, Rich Hill and Andrew Miller are among the other lefties fighting for a spot.
"[Reyes] has a track record -- he's done it," Epstein. "He's a pretty effective left-hander. We were looking at him with a number of other lefties throughout the winter. It looked like he had signed, but that fell through and then he became available on a Minor league deal, and we jumped on it. He has an interesting combination -- the ability to sink the ball and make lefties uncomfortable. We'll see how he's throwing when he gets here."