About an hour before Saturday's game with the Portland Trail Blazers, Washington Wizards coach Eddie Jordan found out that Arenas wasn't going to be available.
Arenas, who had surgery on his left knee in April, missed the game with soreness in his knee.
Everything worked out for Jordan and the Wizards, as Jamison had 30 points and 11 rebounds to lead short-handed Washington over Portland 109-90 on Saturday night.
Jamison's season-high scoring mark enabled Washington to win its fourth straight game -- the first time they've won four straight since Jan. 15-20.
The Wizards began the season 0-5.
"There's nothing good about losing Gilbert. We want him healthy," Jordan said.
Before the game, Jordan said that Arenas and everyone else had participated in a shootaround and everything was fine. But after his talk, Jordan said Arenas and the team's medical staff felt the knee was too sore for him to play.
Jordan expects Arenas to be ready for the Wizards' next game -- Tuesday against Philadelphia.
In stepped Jamison, who had just 21 points in Washington's previous two games -- both wins. Jamison's shooting wasn't spectacular. He was 8-for-19, but he made four 3-pointers -- three in the first half.
"I think guys really got extra focused," Jamison said. "To miss what Gil does on a night-to-night basis is a total blow."
Daniels started in Arenas' place and had 10 points and 10 assists, but it was Nick Young, the Wizards' first-round draft choice, who took advantage of Arenas' absence. After not scoring more than five points in his first six games, Young had 17 points in 14 minutes.
An 11-0 run put Washington up 11-2 in the first 5 minutes. The Trail Blazers, who are 0-6 on the road, were 1-for-9 from the field. Portland then scored the next seven points.
But Jamison, who had six points in the first quarter and nine in the second, helped the Wizards built a 47-38 halftime lead.
Brendan Haywood, who had 17 points and 10 rebounds, began the third quarter with a 3-point play, and Washington extended its lead to 63-44 midway through the quarter on Jamison's 3-pointer.
"We did a good job on both ends of the floor -- offensively -- and especially defensively," Jamison said.
"We played pretty darn well throughout the 48 minutes," Jordan said.
The Trail Blazers have won all their home games and wonder what's wrong away from the Rose City.
"We're more confident at home," Aldridge said. "We're running more and more free at home. On the road, I think we're more hesitant and not playing with as much energy."
Before the game, reflecting on Friday night's Philadelphia loss, Trail Blazers coach Nate McMillan said he was eager to have another game within 24 hours, but after absorbing a second-straight sobering defeat, he may be having second thoughts.
"We just look like we have heavy legs. We look a step slow on both ends of the floor," McMillan said. "We looked kind of the same way [Friday] night."
Arenas has scored 30 or more points in a game against every NBA team -- except Portland. Haywood's double-double was his sixth of the season. He had seven last season. Washington's margin of victory was its largest since beating New Orleans 125-103 on March 17.