Andrew Bynum progresses in recovery

EL SEGUNDO, Calif. -- The overall health of the Los Angeles Lakers' roster took one step forward and two steps back heading into back-to-back preseason games this weekend.

The step forward: Andrew Bynum participated in a series of resistance strength exercises on the sidelines Friday with the aid of trainer Alex McKechnie. It was the first time Bynum worked upright during the recovery process from offseason knee surgery.

"We hope that it's within a week or two that he's on the court with us," Lakers coach Phil Jackson said. "That doesn't mean that he's going to go through a full practice, but he can do some of the things."

Bynum was originally cleared by doctors to return to contact drills and weight-bearing exercises on the knee in late October.

The two steps back: Sasha Vujacic will not play this weekend and will be re-evaluated Monday after suffering a concussion Thursday when an inadvertent elbow from Lamar Odom struck him under his left eye. Vujacic wore sunglasses as he watched Friday's practice on the sidelines.

Luke Walton is also listed as doubtful for the four-team round-robin dubbed the Staples Center Shootout as his right hamstring strain continues to improve.

"Sasha says he's feeling pretty good, actually. He doesn't have blurred vision, he doesn't see lights and they did find a brain when they went in," Jackson quipped.

There was also a step sideways.

A day after completing a full practice with the team and shooting workout afterward, Kobe Bryant did not practice with the team Friday, giving his surgically repaired right knee a day's respite from running up and down the floor. He did participate in an off-court workout, however.

Bryant continues to pace his recovery from the offseason procedure, the third since 2003 on the knee, with the goal of being as close to as 100 percent as possible for the season opener against the Houston Rockets on Oct. 26.

"[He looks] better," Pau Gasol said of Bryant. "I think he's feeling more comfortable, more aggressive and getting into a rhythm out there. Obviously he's testing himself and I like the progress that I've seen as far as movement goes and confidence."

Jackson said he plans to keep Bryant's playing time to "under 24 minutes" on Saturday against the Denver Nuggets. Rookie swingman Devin Ebanks has been playing more guard at practice, with the possibility of filling in some of the backcourt minutes vacated because of Bryant's and Vujacic's injuries.

Dave McMenamin covers the Lakers for ESPNLosAngeles.com. Follow him on Twitter.