Wood had received a cortisone shot on Wednesday, but it apparently didn't do enough for him to avoid a trip to the DL.
Cubs manager Dale Sveum said the shots were helping, but instead he and the Cubs chose to be cautious with the man who entered the season as the Cubs' primary setup man. Wood has underperformed in limited action this season, posting an 11.57 ERA through 2.1 innings.
The injury is retroactive to April 13th, so he could theoretically return as soon as April 28th.
The Cubs recalled left-hander Scott Maine from Triple-A Iowa to take Wood's spot on the roster. In his five minor league appearances, Maine was 1-0 with an ERA of 1.42.
Maine has appeared in just 20 games in his major league career. In 13 games in 2010, Maine recorded a 2.08 ERA to go along with a 1.077 WHIP. He did not achieve the same success in 2011, recording an ERA of 10.29 with a WHIP of 2.286 in seven games.
The setup role in the Cubs' bullpen now seems wide open, at least until Wood returns.
Relievers on the Cubs' roster have seen varying levels of success, so it could very likely be a by-committee type of situation.
Lefty James Russell could slide into that role, with Maine taking over the responsibility of being the lefty specialist. So far this season, Russell has yet to allow a run through 4.2 innings.
Wood's injury shouldn't linger throughout the season, but you never know with the fragile arm of the former flamethrower.