When the air horn sounded Wednesday afternoon, signaling the start of the first Vikings practice of the week, Adrian Peterson reclaimed his old spot at the front of the team stretch and helped lead his limber teammates.

Individual drills soon started, with Peterson standing behind fellow running backs Jerick McKinnon and Matt Asiata in the handoff line. Moments later, he snagged a few passes out of the backfield, once turning upfield on a wheel route. Then it was time to tiptoe through some orange cones. All the while, he wore a bulky brace on his surgically repaired right knee.

Peterson participated in his first practice since tearing his meniscus on Sept. 18 against Green Bay. He was placed on injured reserve after the injury with the special designation that he could return this season.

While he is targeting a return on Christmas Eve against the Packers, his return to practice provided an emotional boost. The Vikings have two wins in their past eight games and must beat the Indianapolis Colts on Sunday to keep their playoff hopes alive.

"I think he's just one of those guys. He has been a leader on this team. Obviously, he's one of the best players in this league, and he has been for quite some time," quarterback Sam Bradford said. "I think just having him back out at practice in the huddle, I think it's a definite lift to our guys."

The question, if and when Peterson does return to game action, is whether he can lift a Vikings offense that has changed a lot since September.

Since we last saw Peterson in a purple helmet, the Vikings have put three offensive tackles on injured reserve, lost their offensive coordinator to a midseason resignation and given their shaky kicker the boot.

With backups manning multiple positions on their leaky offensive line and interim play-caller Pat Shurmur putting Bradford in the shotgun on the vast majority of his dropbacks, this is not the same scheme from Weeks 1 and 2, when Peterson often got a running start on under-center runs.

"Obviously, it's a little bit different than the first couple weeks," Bradford said. "But Adrian's a great player, and I'm sure he'll be able to adjust."

Throwing 84 percent of his passes after taking a shotgun snap this season, Bradford has a gaudy 71.2 completion percentage, most of them within 10 yards of the line of scrimmage, and has a 14-to-3 TD-to-interception differential. His 98.2 passer rating ranks eighth in the NFL.

The running game remains a disaster, though. The Vikings are last in the league at just below 3 yards per carry, and in last week's victory over Jacksonville they twice came away without points inside the 5-yard line because of their inability to inch the ball over the goal line.

At the very least, Peterson on one good leg probably could help them there.

But what about those shotgun runs, the ones that often went nowhere when he was in the backfield the first couple of games this season? Sure, McKinnon and Asiata have received more handoffs out of the shotgun the past three months, but 69.1 percent of their carries still came from under center.

Bradford said that if Peterson returns — remember, just last week the 31-year-old said he wouldn't if the Vikings were eliminated from playoff contention — they will have to find a comfortable balance of what has worked since Shurmur took over in Week 9 and what worked for Peterson in seven Pro Bowl seasons.

But with three games left and zero margin for error, this is not an ideal time for strategic tightrope walking.

"Any chance you get to add Adrian Peterson back to your lineup, I think it's a positive," Bradford said, shrugging off concern. "So I think we'll definitely take him back in the lineup regardless of if it adds any challenges or not."

Coach Mike Zimmer wouldn't bite when asked if there is any chance Peterson could suit up against the Colts. He added that he will worry about how Peterson fits into the league's 31st-ranked offense when the time comes.

The Colts, meanwhile, say they will plan as if Peterson is playing Sunday.

"I think we would be foolish not to," Colts coach Chuck Pagano said.

But even if he does not return Sunday, Peterson's presence at practice appears to have already given his Vikings teammates a much-needed boost.

"We need all the help that we can get," left guard Alex Boone said. "We've got a bunch of guys [hurt] right now and we need all hands on deck."