MANKATO, Minn. -- Tarvaris Jackson has worked hard to quickly return to practice after missing some time with a left knee injury. He doesn't want to fall behind in the competition for the Minnesota Vikings' starting quarterback job.

Tarvaris Jackson , QB
Minnesota Vikings

2008 Statistics
Games/Starts: 9/5
Passer Rating: 95.4
Passing Yards: 1,056
TD/INT: 9/2

But Friday night under the lights, Jackson might have tried to do a little too much. He appeared to aggravate the sprained medial collateral ligament in his left knee when he planted after dropping back to pass, then came up gimpy and limped around for several minutes before returning to action.

"I guess I just wasn't ready for that right now," Jackson said after practice. "But it's fine. It's not bothering me still. It was awkward for me. I think it was just some scar tissue."

Jackson is competing with Sage Rosenfels for the starting job. The players split snaps with the first team during two practices Friday.

"I just felt something pop for a quick second," Jackson said. "But after I walked to the sideline, it was pretty much OK. It's fine."

Vikings coach Brad Childress said Thursday that the passing game had much to improve upon as training camp continues. There were more struggles in the evening practice Friday, but Childress said that was because the team was practicing third-and-long scenarios, a difficult position for the offense.

Childress said he wasn't ready to "slap a grade on" the quarterback competition one week into training camp.

"Obviously (Jackson) has missed time, so it wouldn't be fair to sit there and say, 'This guy's ahead by virtue he had five more practices,'" Childress said. "It's a good competition. It's all headed toward cumulative work here during practice and then I want to watch them compete with the lights on."

Rosenfels looked sluggish in the early going, but he appears to have grown more and more comfortable with the offense and his receivers in the last few practices. Childress said it's a natural progression for a player whom the Vikings acquired in a trade with the Houston Texans during the offseason.

"I don't think he's having to think quite as much," Childress said. "But yeah, he's moving along. All three of those guys (including John David Booty) are moving along. We'll see how far along here in about a week."

The Vikings open the preseason next Friday against the Indianapolis Colts.

Copyright 2009 by The Associated Press

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