ALLEN PARK -- Lions running back Kevin Smith underwent surgery on his thumb today (Wednesday) and will not be available to play on Sunday at Dallas.

Smith has provided a spark to the mostly anemic run game, especially in recent weeks. He will be missed.

Coach Jim Schwartz did not give a timetable for his return, but said he will not play Sunday. Smith injured the thumb in Sunday's loss at Buffalo.

Running back Aaron Brown, who was inactive the last six games, will be added to the mix.

Smith missed the first three games of the season because he was coming back from ACL knee surgery. In the last six games he has carried the ball 34 times for 133 yards and had 11 receptions for 123 yards.

His absence is a hit for the Lions’ rushing offense which is ranked 30th in the NFL.

(Follow me on Twitter @PaulaPasche.)