MANKATO, Minn. -- Tarvaris Jackson has been hurt a lot in his short career and this time he feared the worst.
His left leg hit by a 300-pound teammate over the weekend, Jackson initially wondered if his anterior cruciate ligament was damaged, the dreaded knee injury that's sure to end a season before it starts.
To his relief -- and the Minnesota Vikings' -- Jackson was diagnosed with only a mild sprain of his medial collateral ligament. It was welcome news after the scary sequence in Saturday's practice when defensive tackle Letroy Guion got tangled in the line and rolled on the ground into the oft-injured quarterback.
"'Please, no,'" Jackson said Tuesday, recalling his reaction.
This is a team that learned only last week that Brett Favre wasn't coming out of retirement to play for Minnesota. His decision put the spotlight squarely on Jackson and Sage Rosenfels in the competition to start for a team that's talking about winning the NFC championship.
Jackson shrugged off the possibility of falling behind Rosenfels at practice.
"Obviously, the guys are getting a lot more reps with the offense and everything," Jackson said. "But I'm still in the meeting room studying every day. I'm still in there watching film, watching their mistakes, watching things that they are doing pretty good and just try to learn from things that they are doing. I'm just not able to do it physically right now, but I'm still tuned in mentally."
Jackson threw a bit Tuesday and simulated some drop-backs during the morning practice under the watch of athletic trainer Eric Sugarman. He is wearing a special brace for more stability and mobility, and coach Brad Childress said he was pleasantly surprised to see what he called rapid progress in Jackson's recovery.
"Just watching him throw and move his feet around, he doesn't seem to be that drastically affected," Childress said, declining to speculate on when Jackson would return to full participation in practice.
Jackson is still walking gingerly, but he said he's "pretty sure" his knee will be 100 percent healthy in time for the first preseason game against the Indianapolis Colts on Aug. 14. Last year, Jackson hurt his right knee in an exhibition game and missed the last two preseason games, but he said this injury isn't as severe and that he has already recovered much faster than last time.
Entering his fourth NFL season, Jackson has spent plenty of time in the training room. He also hurt his right knee as a rookie and then in 2007 missed two games with a strained groin, one with a broken finger and another with a concussion.
With time running out for him to prove himself as worthy of the starting job, Jackson said he's not concerned about being branded as injury prone. Just "fluke stuff," he said.
"Just getting my share like every other guy. It happens to everybody. It's a contact sport," he said. "Just try to avoid it as much as possible by training and everything, but it's going to happen."
The Vikings also waived wide receiver Aundrae Allison, their fifth-round draft pick from two years ago. He had success as a kickoff returner, but the Vikings have added rookie Percy Harvin and last season's sixth-round draft pick Jaymar Johnson is emerging as a solid player.