Greg Jennings is absolutely certain he will play in the playoffs. A “huge day” on Wednesday confirmed it for him.

“Whoever we’re playing, I’m on the field,” Jennings said after practice, speaking to reporters for the first time since injuring his knee more than three weeks ago. “No doubt.”

Jennings’ confidence lies in the rehab plan he has gone through with the training staff, which has proceeded as well as he could have expected. He said the target all along was to get the knee in shape for the regular-season finale against Detroit, even though he presumably wouldn’t play if nothing was at stake for the team.

That would allow the bye before the first playoff game to provide a two-week “insurance policy” to clear some mental hurdles, an important consideration for a player who had missed consecutive games only once in his career, and not since Weeks 1 and 2 of the 2007 season. Jennings missed the last three games of this regular season, equaling the total number of games he had missed due to injury in his first five years in the league.

“If I had to play last week, I would have played last week,” Jennings said. “But the more time you get, you try to take advantage of it.”

Jennings was back at practice on Wednesday, the first of the Packers’ two workouts this week. He ran some routes “on air” last week, and on Wednesday he got involved in the competitive drills against defenders. He called it a “huge day.”

“Just to know that I can react and respond to a guy up in my face and still be able to beat the jam, and kick it in another gear when the ball is in the air,” he said. “All that took place today.”

As for that extra gear, Jennings has regularly found it in the playoffs. In seven career postseason games, he has topped 100 yards three times and caught five touchdown passes.

Entering the playoffs with a healed and rested body could mean a big postseason is in store. Jennings had 949 receiving yards and nine touchdowns in 13 regular-season games before being sidelined.

“I was telling the guys it’s really been a blessing in disguise, because late in the season, that’s when the bumps and bruises start to nag and just stay, and you have to fight through everything,” Jennings said. “For myself, I’m as fresh as I’ve been at the end of the season.”

He apparently showed that on the practice field.

“He looked awesome,” said tight end Jermichael Finley, who has come back from a couple of knee injuries already in his young career. “The thing is … he’s got to take that first hit and pop up. It’s all a mind thing, and I think Greg is a strong enough person to handle that. I think he’s going to come back strong.”

Another offensive weapon looking to do the same is running back James Starks, who missed three of the last four regular-season games with ankle and knee injuries.

Starks has not been cleared to practice, yet, but was continuing his rehab. He, along with center Scott Wells and inside linebacker D.J. Smith, did not practice on Wednesday. Head Coach Mike McCarthy declined to comment on any absences or injuries until the next official injury report comes out next week.

Not fully healthy since the Tampa Bay game in Week 11, Starks admitted the second half of the season has been frustrating after he topped 500 rushing yards through the first nine games. But he understands that “this is what counts,” meaning the playoffs, and his position demands that he be at full strength and speed to be successful.

“As a running back in this league, you get hit all the time and you have to make a cut on a dime and make people miss,” Starks said. “All the good running backs in this league that break tackles and all that, you need to be healthy to be productive.”

On the other side of the ball, the Packers have been looking for more production at the outside linebacker spot opposite Clay Matthews, and it appears Brad Jones’ performance last week against Detroit has given him the inside track to the starting job for the playoffs.

Jones posted a season-high six tackles, including a sack, in the Lions game. That was his most extensive playing time on defense all season as he, paired with Frank Zombo, rotated with Erik Walden and Vic So’oto.

Primarily a special-teams player so far this season, Jones is tied for second on the team in coverage tackles with 11. Injuries last year led to him being placed on injured reserve in October, which hindered him from capitalizing on a strong finish to his rookie season. In 2009, the seventh-round pick had four sacks in seven starts down the stretch in place of an injured Aaron Kampman, and Jones believes he can perform like that again.

“If this window of opportunity opens up, I think I’ll show them something they need to see,” he said, and he sounded as confident in the defensive unit as a whole, too.

“We have great players, and I think when this playoff game comes around, we’re really going to step up. Really step up.”

Additional coverage - Jan. 4