St. Louis, MO -- (Sports Network) - St. Louis Rams running back Steven Jackson will not play Sunday against the San Francisco 49ers because of a strained right thigh muscle.

"Steven's [Jackson] out, he's not traveling [to San Francisco]," Rams interim coach Jim Haslett said on Friday.

Jackson was hurt during the October 19 game against Dallas, despite rushing for 160 yards and three touchdowns, then missed two of the Rams' next three games, including last Sunday's 47-3 blowout loss to the New York Jets.

For the season, Jackson has 525 yards on 128 carries with four touchdowns and has added 25 catches for 259 yards.

Antonio Pittman, who ran for a mere 28 yards on 13 carries in the setback to New York, and Kenneth Darby will likely see the majority of carries out of the backfield in Jackson's absence.