"Detroit Lions running back Kevin Smith will undergo thumb surgery Thursday and miss Sunday's game against the Dallas Cowboys.

Smith suffered a thumb injury late in the first half of last Sunday's loss to the Buffalo Bills. He missed three games earlier this year while recovering from 2009 knee surgery but has served as Jahvid Best's primary backup since early October.

"Kevin has been extremely tough in his dealing with a lot of different issues and his giving us a spark and things like that," Lions coach Jim Schwartz said. "But there's a big difference in dealing with sore knees and ankles and shoulders and hamstrings, all those things that running backs deal with, and dealing with a thumb when you're talking about ball security and being able to catch the ball and things like that. So he's very disappointed, but it's something that needs to be done.""