At the time they were dealt, here were their stats:
Gonzalez: .300/.343/.469
Crawford: .282/.306/.479
Beckett: 5-11, 5.23 ERA
Those are hardly numbers that will be difficult to replace.
Gonzo's .812 OPS is not all that great to be honest. Those numbers can be pretty easily replaced by any number of players, be it a trade for a guy like Corey Hart, or signing someone like LaRoche or Napoli.
Crawford only played 31 games, but regardless, Torii Hunter, Shin Soo Choo, Melky Cabrera, Justin Upton, Cody Ross, etc can replicate Crawford's numbers pretty easily.
It's not going to be any FA acquisitions or trades that push this team into a contender. It's going to be the rebound by Jon Lester and Clay Buchholz, and maybe a little bit of a contribution from a Matt Garza/Anibal Sanchez/etc that we acquire externally.
If Lester and Buchholz return to form (3.30-3.50 ERA), this team is going to be right in the mix, no doubt. It isn't going to take a bunch of Josh Hamilton type signings to get them where they need to be. It's going to take pitching, health, and guys just playing career norm baseball.
Pedroia and Ellsbury will both almost certainly rebound, Lavarnway will be much better than Salty, as OBP is heavily favored over SLG, Middlebrooks and Ortiz will be healthy again.
And I really think that both Lester and Buchholz figured out their mechanical issues (Buch earlier than Lester), and with Farrell as their manager, I think he'll be a big help.
Just a quick reminder, last time Farrell was with the organization, Lester had 19 wins, Buch had 17 wins, Lackey had 14 wins, and they all had decent to outstanding ERA's. Not saying he's a miracle worker, but at the same time I think the SP will have a lot more comfort with their coaching staff this year than they have in a while.