MILWAUKEE – Sitting around the house for all those offseason months, Chris Andersen didn’t believe he would play this season. He kept lifting weights, kept shooting in the gym, but his expectation was to take the year off, fully heal the right knee on which he had arthroscopic surgery over the summer, and sign with an NBA team for next season.

When Andersen made enough progress with his knee to play this season and learned about signing with the Miami Heat, he felt grateful for another opportunity, a sense of rejuvenation after being amnestied by the Denver Nuggets in the offseason. Many teams could have used Andersen to bolster their frontcourt, but none were as proactive as the Heat to add the dimension they’ve lacked: A 6-foot-10, long-armed big body whose motor is endless even at 34.

“Going back and forth on [if] I was going to play, I really didn’t expect to play this season,” Andersen told RealGM. “I was going to let my knee heal up all the way before I could step foot back on the court and do some basketball stuff. … There ain’t no shape like getting in basketball shape, unless you’re playing basketball. I could be in the greatest shape that I could be in, but if you’re not in basketball shape, then you’re just two steps behind.”

The Heat held extensive searches as far back as last offseason to add an athletic frontcourt player, bringing in big man after big man for workouts. No one’s upside with the team intrigued Miami management as much as Andersen.

For now, Andersen has moved past Joel Anthony as the Heat’s first big man off the bench, and he continues to play catchup on schemes and offensive sets, spending time watching tape with the coaching staff before games. His knee flared up at times upon his start with the Heat, but he’s steadily increased the strength in the knee, steadily regaining full confidence in it. Gradually, Andersen has felt more comfortable on the court, with 10 points and five rebounds in 16 minutes Wednesday and five points and five rebounds in 16 minutes Friday.

“The [Heat] have a great training staff on board,” Andersen said, “and they definitely kept me in the training room, kept ice on it, kept stim on it, kept plugging away at the knee that became inflamed with all the activity.

“So over the past couple months, I’ve really gotten my body to where it has endured all of the beating and banging that I’ve been doing. I’m pretty much back into my old swing of things.”

Erik Spoelstra experimented frequently with the Heat’s rotation early in the season to find the solution he’s comfortable with over these next two to four months. There’s no plan in place to increase Andersen’s minutes – instead staying where his playing time has been recently, around 15 to 20 minutes – and the energetic big man appears part of the reserve group that Spoelstra will trust in the playoffs.

Still, Spoelstra primarily played four bench players throughout last season’s title run, and the minutes of Andersen and Mike Miller could fluctuate depending on matchups. In Friday night’s 107-94 win over the Bucks to push the Heat’s win streak to 21 straight, Spoelstra also closed out the final five minutes with his potential crunch-time lineup come playoff time: LeBron James, Dwyane Wade, Ray Allen, Shane Battier and Chris Bosh.

Andersen played a critical reserve role in playoff runs with the Nuggets, most notably in the trip to the Western Conference Finals in 2009. In his 11th season, he doesn’t know how much longer he wants to play. He’ll know whenever his activity runs empty, Andersen guesses.

“I ain’t no anchor, man,” Andersen said with a laugh. “These are all veteran guys and they know what they’re doing. I’m just thrilled to be here and being part of the defending champions and having an opportunity to win this again with this group of guys. It’s amazing to be in that situation, not taking anything for granted and staying on what I’m doing.

“It’s real special to me, real unbelievable getting the opportunity to win a championship.”