Arenas sprained his left knee in a collision with Gerald Wallace in the first quarter of Wednesday night's 108-100 loss to the Charlotte Bobcats.
The three-time All-Star will have an MRI exam today to determine the extent of the damage, but the recovery time from such injuries is usually measured in weeks, not days, and the Wizards have only eight games left in the regular season.
He was just standing there, settling into rebounding position as Wallace drove baseline. When Wallace threw up one of those incredible, off-balance reverse layups, he crashed inadvertently into the left leg of the Wizards' guard.
The Wizards earlier this week lost All-Star forward Caron Butler to a broken hand.
Wallace finished with 27 points, 12 rebounds and eight assists to lead the Bobcats.
ORLANDO, Fla. - Chris Bosh scored 28 points, including five free throws down the stretch, to lift Toronto over Orlando.
Hedo Turkoglu shook off a recent shooting slump to score a career-high 37 points for the Magic, but missed a potential game-tying 3-pointer.
Anthony Parker added 20 points for the Raptors, Joey Graham scored 19 and T.J. Ford had 16 points and eight assists.
HOUSTON - Jason Richardson scored 27 points, including seven 3-pointers, and Golden State took advantage of Tracy McGrady's absence to beat Houston.
Baron Davis added 25 points and 10 assists for the Warriors.
Luther Head hit seven 3-pointers and scored 30 points, both career highs, filling in for McGrady, who left in the first quarter with a stiff lower back.
AUBURN HILLS, Mich. - Kirk Hinrich scored 29 points, Luol Deng added 22 and Chicago beat Detroit.
Ben Wallace missed the Bulls' game against his former team after going to the hospital with a sinus inflammation.
The game almost took an ugly turn with 8:12 left. Detroit's Richard Hamilton and Chicago's Tyrus Thomas were ejected with two technical fouls while play was stopped with 8:12 left after exchanging heated words and being separated by teammates. While walking off the court toward their locker rooms, both players had to be separated again.
EAST RUTHERFORD, N.J. - Backup forward Bostjan Nachbar scored 26 points and New Jersey overcame a second-quarter drought for a victory over injury-ravaged Atlanta.
Vince Carter added 24 points and eight assists, and Jason Kidd had 10 assists as the Nets won for the fourth time in five games and sent the Hawks to their seventh straight loss.
NEW YORK - Andre Iguodala scored 18 points and blocked Stephon Marbury's potential winning 3-point try, giving Philadelphia a victory over New York.
Marbury scored 28 of his 30 points after halftime, helping New York turn a double-digit deficit into a nine-point lead.
MILWAUKEE - Earl Boykins scored 32 points to help Milwaukee snap a seven-game losing streak by beating Boston.
The teams dressed only nine players each before Boston's Delonte West left in the third quarter because of a sprained ankle.
OKLAHOMA CITY - Bobby Jackson scored seven of his 18 points in overtime to help New Orleans overcome its lowest-scoring fourth quarter in franchise history and defeat Seattle.
David West added 18 points and 14 rebounds, and Rasual Butler scored 16 as the Hornets had six players in double figures.
Rashard Lewis led Seattle with 27 points and 10 rebounds.