Anderson got the start and had 14 points and seven rebounds in 23 minutes of action while Richardson came off the bench and had eight points and four rebounds in 25 minutes.
Prior to the game Hedo Turkoglu (eye) was announced as out for the regular season.
Monday night marked the third game Howard has missed in two weeks after sitting out losses to the Pistons and Denver last week with back issues.
Van Gundy said Howard struggled in the fourth quarter of the Magic's win over Philadelphia on Saturday, having trouble sitting down during timeouts. He finished with 20 points, 22 rebounds and a season-high six assists.
"What he did the other night was phenomenal," Van Gundy told reporters Monday, according to the Orlando Sentinel. "He couldn't even sit on the bench comfortably at a timeout. He couldn't get loose. They were treating it all the time. ... But the price to him was that the spasms and everything have gotten worse. He did it at a personal price."
Glen Davis started in Howard's place and finished with 16 points, 16 rebounds and five assists while playing a game-high 35 minutes.
Howard will travel to Washington on Tuesday, but is also doubtful for that game.
The plan is for him to rest Wednesday and Thursday and hopefully be back for Friday's home game against Atlanta.
"Then there's optimism that by Friday he'd be back to 100 percent," Van Gundy said. "The good part of it is it's just what they call 'soft-tissue' stuff. He doesn't have a bulging disk or a herniated disk or any structural stuff. So that's the positive part of it."
Information from The Associated Press was used in this report.