After going 23-14 with Randolph sidelined with a torn MCL, Memphis (25-19) has dropped two of three since his return, beating Washington while losing to Toronto and Sacramento. The 2010 All-Star made his first start since New Year's Day in Tuesday's 119-110 loss to the Kings, finishing with 13 points on 6-of-15 shooting and seven rebounds.
Rudy Gay had 23 points and Marc Gasol added 15 points, 10 rebounds and eight assists for the Grizzlies, who have lost four of six after winning nine of 10.
"I don't want to talk about any individual person," Grizzlies coach Lionel Hollins said. "All I want to talk about is that we got our butts kicked because we did not play hard and did not play together."
Memphis, which has struggled to find the right chemistry since Randolph's return, could again have some trouble with the addition of a new player.
The Grizzlies signed Arenas, waived by Orlando in December through the new amnesty clause, on Tuesday for the remainder of the season. The 30-year-old Arenas has averaged 21.2 points and 5.4 assists in his nine-year career, but knee injuries have prevented the three-time All-Star from again living up to the "Hibachi" nickname he bestowed upon himself for his ability to heat up quickly.
Arenas averaged 10.8 points on 36.6 percent shooting last season for Washington and Orlando.
Memphis isn't expecting Arenas to perform like he did in his prime, but he should provide depth behind point guard Mike Conley and shooting guard Tony Allen.
Conley and Allen each struggled mightily in the Grizzlies' lone meeting with the Trail Blazers, a 97-84 loss in Portland on Jan. 24. The two combined for 14 points on 7-of-23 shooting as Memphis fell to the Blazers for the fourth time in five games.
Portland (21-25) is hoping to rebound from Tuesday's 116-87 loss to Milwaukee, running its average margin of defeat in its past five losses to 24.4 points. LaMarcus Aldridge had 21 points and 12 rebounds and Wesley Matthews also scored 21 for the Blazers, who've dropped nine of 12.
"We got to play with more effort," Aldridge said. "We got back-doored like four or five times. We've got to fight through screens, our bigs have to be up on the screens. I feel like we didn't do that. We just worried about trying to outscore them. Our defense wasn't there."
Portland hasn't had much of a defensive presence lately, surrendering at least 111 points in three of its last four games. The Blazers are allowing an average of 103.8 points in 12 games since the All-Star break after giving up an average of 92.5 in their previous 15.
That lack of defense usually spells certain doom for the Blazers, who have lost their last 16 games when allowing their opponent to reach the century mark.
The Grizzlies, meanwhile, have scored at least 110 points in three of their last four but have lost all three -- two in overtime. They had won their first 12 games when cracking triple digits.
Gay is leading Memphis' recent scoring surge by averaging 26.5 points in his last three games -- 7.3 better than his team-leading average.