Left guard Daryn Colledge is considered the Packers' emergency left tackle should anything prevent Chad Clifton from playing, and on Tuesday Colledge worked both practices at left tackle while Clifton rested his sore knees.

Until Tuesday, Junius Coston and Orrin Thompson had shared most of the snaps at left tackle when Clifton would take a practice off. But Coston sat out the morning practice Tuesday with a bandage on his knee, and Thompson was bothered by a back injury, so Colledge filled in at left tackle with the No. 1 unit. That left rookie Allen Barbre at left guard, where he practiced on Monday while Colledge rested a minor back sprain.

"It's an excellent opportunity for me to get out there and look at the defense in a different way," Colledge said. "The tackle has a whole different opinion of what the defense looks than the guard does. I think it makes me a better guard to see what the tackle's going through against different defenses. It allows me to think beyond just what the guard has to do every day."

It also allows him to get ready should anything happen like last year in Miami, when Clifton came down with a nasty stomach virus the night before the game, and Colledge was told an hour before kickoff he'd be at left tackle blocking the Dolphins' premiere pass rusher, Jason Taylor.

Colledge is no stranger to left tackle, having played there throughout his college career at Boise State, but protecting the blind side of quarterback Brett Favre is a job all its own. Colledge struggled early against Taylor, who got two early sacks last year, but then settled down, and with some adjustments in the protection scheme the Packers kept Taylor quiet the rest of the day.

Colledge said offensive line coach James Campen told him he trusts him to play left tackle in a pinch, but it never hurts to do some work there.

"For my own comfort, it's nice to have a day like today where I can get out there and rep it out and get in the mix with those guys," Colledge said. "I'd like to have a little more experience than I had last year when I got thrown in there in Miami."

Palmer takes center stage

Tony Palmer, who has worked primarily at guard as a backup offensive lineman, appears to have taken over the backup center job. Palmer was working at center with the No. 2 offensive line in Monday's practice, and that continued through both of Tuesday's workouts.

Head Coach Mike McCarthy said Palmer started working at center late last season on the scout team, and he's continuing to learn the position. In college at Missouri, Palmer played guard but did learn how to call blocking assignments. His next step at center is to be an effective blocker against linebackers running downhill toward the ballcarrier.

"He's a very powerful player on the first level," McCarthy said. "The thing he needs to work on and get used to, because schematically he hasn't done it before, is the second-level blocking."

Gutting it out

Tight end Zac Alcorn has been battling a blister problem with his feet, but he played through it in last Saturday's intrasquad scrimmage and has continued to practice this week.

He's been desperately needed because of the injuries at tight end. Tory Humphrey already is on injured reserve (ankle), rookie Clark Harris went out late last week with an ankle injury and dropped out Tuesday night with a hip flexor. Also, Bubba Franks (eye) just returned to practice on Monday after missing a few days.

On Tuesday morning, Alcorn and Donald Lee got most of the snaps with the No. 1 offense during some red zone work. Alcorn caught a touchdown pass from Aaron Rodgers, while Lee made a nice grab with good footwork in the back of the end zone with linebacker Desmond Bishop trying to strip the ball out.

"It felt good. I like to get in there and build chemistry with the first-team guys and stuff, and it did feel good to catch some balls out there," Alcorn said.

"The tight ends have been getting a lot of reps, the guys that have been out there in practice. It's been really good for us. It's also beating us down a little bit, but we have to keep pushing, I guess, keep grinding through."

In the evening, Alcorn got in another strong workout, as did Franks. McCarthy gave Lee the night off because of all the reps he had taken lately.

{sportsad300}Kickers keep at it

The coaching staff continues to mix it up on kickers Dave Rayner and Mason Crosby, and Tuesday it was run-on field goals, where the kicking unit has to rush onto the field and get off a quick attempt.

The logistics of the drill looked fine for both, and in the morning practice Rayner hit his attempt from 40 yards out while Crosby missed wide left. In the evening during the run-ons, Rayner missed wide left from 43 yards, and Crosby was good from the same distance.

"Every day it's something new," Crosby said. "They're throwing us in different situations to see how we react. It's a challenge every day."

In a series of kicks in the evening, both kickers were 4-for-4 from 30 to 37 yards. Then from 47, Crosby was 1-for-3, with one blocked and another wide right, but McCarthy said the edge rusher was offsides on the block. Rayner missed wide right from 47.

Catch of the night

In the final team period of the evening practice, receiver Donald Driver made a spectacular diving catch in the end zone just before sliding out of bounds on bullet throw from Brett Favre. Driver's body was completely horizontal when he hauled it in, and his feet and knees dragged in bounds, so it was a completed catch and touchdown.

Injury, participation update

Quarterback Brett Favre took the morning practice off with soreness in his ankle, but McCarthy said it wasn't the ankle he had surgery on during the offseason. Favre returned for the evening practice and had no setbacks.

Wide receiver Greg Jennings remained out with a hip flexor, though McCarthy hopes he can practice on Thursday. Offensive lineman Tony Moll (stinger) and defensive end DeVon Hicks (groin) also remained out.

Linebacker Rory Johnson (side) returned to practice in the evening.

Defensive tackle Justin Harrell dropped out of the evening practice with a groin injury, as did fellow defensive tackle Ryan Pickett (knee) and running back DeShawn Wynn (quad).