His body has started to rebel. The price compounds for having a nickname like Crash, and aches and bruises that used to wash away with adrenaline now carry into the next day.

But Gerald Wallace also is playing the fewest minutes since his late teens at the end of Sacramento’s bench, and the unspent energy keeps him up late after games.

The frustration from those early years has returned, too. He accepted coach Brad Stevens’ request to come off the bench, rationalizing that it was the right thing at this stage in his career.

But the Celtics are losing, and the assignment grates. Wallace built a career sacrificing his body, playing hard and putting defense first, and he sits on the bench stewing at the thought that some teammates aren’t making the same investment.

This isn’t a pleasant segue into the latter years of a career already in its 13th season. He’s 31, and his body feels like 40. He’s probably stuck here with an untradeable contract. He keeps speaking out, trying to lead. Then comes another night when someone doesn’t attack a loose ball or rotate on defense.

Wallace said it after a particularly embarrassing 129-98 loss in Denver on Jan. 7: Words are empty. He said it with even more disillusionment during an interview in San Francisco last week.

“You’re sitting, only playing 17 or 18 minutes a game,” Wallace said. “You’re watching, you know you can still play, and you watch guys in front of you who don’t play with effort, don’t respect the game and don’t think team first. It kind of frustrates you and (ticks) you off. You have to deal with it.”

His pride, his identity as the one Charlotte fans nicknamed Crash, has been insulted.

“This season is a slap in the face, having to change my game and fine-tune it,” he said. “First of all, it has to come mentally. You accept your situation, but there’s two sides to your brain. One side is fighting the other side because of the predicament you’re in. You feel you can still perform at the level you always have, but at the same time, you’re doubting yourself.”

Physical toll grows

Players filtered down for a morning shootaround in the San Francisco hotel gym last week. Most went onto the floor and started shooting, but Wallace sat on a chair and braced himself as Celtics trainer Ed Lacerte started kneading his right shoulder, injured during a fall three nights earlier in Denver. With each dig from Lacerte’s fingertips, Wallace grimaced, twisted his neck, glared at the floor.

These pains and kinks become permanent. He’s had a career of crashes but easily can name the worst, the most insane.