Steven Jackson will play Thursday night for St. Louis Rams

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St. Louis Rams running back Steven Jackson is a go for Thursday night's game against the 4-0 Arizona Cardinals (NFL Network, 8 p.m. ET) despite a sore groin, according to a team source.

NFL Network's Rebecca Haarlow, who's in St. Louis for Thursday's NFC West showdown, also reported Wednesday that Jackson said he'd be ready to play.

Jackson had seven consecutive 1,000-yard rushing seasons entering 2012, but he's off to a slow start after four games, with 59 carries for just 195 yards and no touchdowns. He has been listed as questionable for the last three games, but so far he has yet to miss any action.

UPDATE: Jackson, as expected, was declared active the Rams' showdown with the Cardinals, the team announced Thursday.