Because he can play both third base and first, Youkilis gives Manager Dave Johnson infield depth and flexibility.
Youkilis finished third behind teammate Dustin Pedroia in balloting for the 2008 American League MVP after a season in which he batted .312 with 29 home runs and 115 RBI.
With his glove, mostly at first, he committed only four errors in 1,014 total chances for a .996 fielding percentage.
Other Boston players who could be available for the world classic are Pedroia, closer Jonathan Papelbon, and left-handed starter Jon Lester, with third baseman Mike Lowell playing for Puerto Rico if he has recovered from offseason hip surgery, and 2007 MVP Daisuke Matsuzaka pitching again for Japan.
All would miss considerable time during spring training.
"I don't know how it's going to impact us yet," Manager Terry Francona said recently. (But) It's not perfect."