Michael Robinson was told he wasn't good enough after four seasons with the San Francisco 49ers. Since joining the Seahawks, the former Penn State quarterback has become a key member of the team's offense.

RENTON — Michael Robinson doesn’t need any outside motivation on the field; the Seahawks running back considers himself a self-driven guy. But some extra fuel came rather bluntly during the exhibition season.

Back in August, Robinson was a fourth-year player with the San Francisco 49ers. A couple of days before the team’s first exhibition game, running-backs coach Tom Rathman approached him with some harsh words.

“He said, ‘You’re not good enough and I don’t think you can play in this league,’ ” Robinson recalled, “and he said, ‘I’m not the only one that feels that way.’ “

Stunned and hurt, Robinson went on to play all four exhibition games for the team that drafted him in 2006, but he was released shortly afterward. His job was lost, but instead of sulking, the 27-year-old sought to prove the 49ers wrong.

Three months later, now a proud Seahawk, Robinson continues to make that case on Sundays. The Seahawks like what they have found in Robinson’s unique skill set and growing role in the offense.

Running-backs coach Sherman Smith praises Robinson’s combination of physicality, attitude and intelligence.

“He analyzes everything like a quarterback as he prepares,” Smith said.

It’s not hard to see why. Robinson was a standout quarterback at Penn State — he finished fifth in the Heisman Trophy voting in 2005 — and took pride in studying the game. The way he plays now, however, is hardly quarterback-ish. The 6-foot-1, 223-pounder exhibits a smack-you-in-the-mouth style as a blocking back that’s as much brawn as brain.

His versatility and aggressiveness, which benefits both the offense and special teams, is highly valued by Seahawks coaches. Offensive coordinator Jeremy Bates describes Robinson succinctly: “Intense. Loves the game. Good football player.”

After missing five games with a hamstring injury, Robinson returned in Week 13 against the Carolina Panthers to help the Seahawks to their best rushing game of the season (161 yards) in a 31-14 win. Last Sunday, against his former team, Robinson led Seattle in rushing, albeit in a lopsided defeat at San Francisco.

Ground success before his return had been hard to find.

“There was a lot of talk about, ‘Why can’t we run it? Why can’t we run it?’ ” said quarterback Matt Hasselbeck. “You can’t say it — or no one wanted to say it — but (if) you don’t have a fullback on your roster, it makes it a little harder, especially in short-yardage and goal-line situations. Having him back is huge.”

These days, as opposed to college, Robinson rarely sees the ball. And while blocking doesn’t exactly net the same fanfare as getting 25 touches a game, he’s comfortable with the role. His self-worth isn’t determined by earning headlines or starring in fantasy football.

“My gratification,” Robinson said, “is when Marshawn (Lynch) or Justin (Forsett) or Leon (Washington) comes to me and says, ‘Good job, man. We couldn’t have done it without you.’ “

Notes

• Coach Pete Carroll said veteran Chester Pitts will start at left guard against Atlanta and Mike Gibson will move to right guard, replacing Stacy Andrews. That would give the Seahawks their ninth different offensive line to start a game this season.

• Receiver Brandon Stokley (hamstring) and cornerbacks Roy Lewis (knee) and Walter Thurmond (hamstring) are questionable. Carroll said he expects Stokley to play, Thurmond to sit and Lewis to be a game-time decision.

• Receivers Mike Williams (ankle) and Ben Obomanu (hand) are expected to play.

Joshua Mayers: 206-464-3184 or jmayers@seattletimes.com