Jackson said Wednesday the injury is trivial and that trainers are just being cautious. He plans on fully participating in Thursday's practice.
Jackson joked that he was hurt "getting out of bed, man," followed by his trademark guffaw, then amended that evaluation to "general soreness."
"His mindset is he'd like to get some plays in," Spagnuolo said. "But we'll see."
This preseason is a bigger deal than usual for Jackson because he's learning new offensive coordinator Josh McDaniels' system. Jackson totaled nine carries for 42 yards in the 2010 preseason but said he'd like to play as long as the first string goes in Saturday night's game against the Tennessee Titans.
"We're all fairly new to it, so you just want to make sure you're executing the plays and doing the things coach McDaniels wants," Jackson said.
St. Louis has upgraded the offense during free agency, signing guard Harvey Dahl, wide receiver Mike Sims-Walker and backup running backs Cadillac Williams and Jerious Norwood. Safe to say Jackson approves.
"I'm very excited about where we're going as an offense," he said. "I'm anticipating a big year not only for myself but for the team as well."
Wide receiver Donnie Avery, the team's best deep threat when healthy, returned to practice after shaking off knee soreness related to surgery last preseason. Avery hasn't been on the field much.
"We just figured why set him back? That's why we kind of shut him down," Spagnuolo said. "I think it was the right thing to do because I think he'll start to surface now.
"It's been a long time since Donnie's been out there, so I'm sure he's chomping at the bit."
Avery was a second-round draft pick in 2008 and totaled 100 catches with eight touchdowns his first two seasons.
Sims-Walker saw limited time in practice, and Spagnuolo wasn't sure if the receiver would play against the Titans. Spagnuolo all but ruled out Sims-Walker (groin) earlier in the week.
Offensive tackle Rodger Saffold (back) and tight end Mike Hoomanawanui (concussion) returned to practice. Spagnuolo said offensive lineman Roy Watts decided to go home.
Copyright 2011 by The Associated Press