"He's human, he bleeds," quipped Celtics coach Doc Rivers. The 36-year-old Allen is off to another hot start this season, averaging 20 points per game while shooting 56.5 percent from the floor overall and 61.1 percent from beyond the 3-point arc.
"We told him not to come," said Rivers. "This morning, I guess he got up and tried to go to shootaround. (Team trainer) Eddie Lacerte told me how he was feeling. We told him to stay away and, if he felt better tonight, to come (to the game). Then when he didn't feel much better, we told him to stay at home. The flu or whatever is going around from what I hear. So we'll see if we can avoid it."
Williams landed on the floor and stayed down for a brief period. He eventually walked off the court with the help of trainer Tim Walsh and was favoring his right side at the time. He sat on the bench, but returned to shoot the ensuing free throws and played the rest of the game.
Williams told reporters that he had X-rays on his ribs, but they were negative. He said his status is day to day.
The two-time All-Star is averaging 17.3 points, six assists and 3.8 rebounds per game for the Nets (1-5), who have lost five straight.
MarShon Brooks started in Williams' place. Brooks currently ranks second among rookies in scoring, at 13.7 points per game.
However, Brooks twisted his ankle at the end of Wednesday's first half. He played through it, but left late in the fourth. An MRI revealed that Brooks has a sprained ankle and is day to day. In his first-ever NBA start, Brooks scored a team-high 17 points on 7-for-16 shooting.
"I'm good y'all," read a post on Brooks' Twitter account. "My scared than hurt."
Power forward Kris Humphries, who has a sprained left shoulder, missed his second straight game, Johnson told reporters on Wednesday.
Humphries had a cortisone shot in his left shoulder, according to the Newark Star Ledger. He told the paper he would practice Thursday and be able to play Friday.
In five games, Humphries is averaging 12.4 points and 10 rebounds. He also sat out Monday night's loss to Indiana. An MRI taken Tuesday revealed the sprain.
Mike Mazzeo is a regular contributor to ESPNNewYork.com. Information from ESPNBoston.com's Chris Forsberg was used in this report.