Clippers without Danilo Gallinari fall to the Trail Blazers 125-104

There was a stretch of possessions in the third quarter when the Clippers could’ve really have used Danilo Gallinari.

Arguably the team’s best player, Gallinari could’ve helped stifle the Portland Trail Blazers’ momentum as it steadily picked up in the second half. Maybe it would’ve been the calm release and high-arching shot that would’ve snuffed out a run. Maybe it would’ve been quicker-than-you-expect feet stopping a Damian Lillard drive.

The way he’s been playing, it’s a safe bet that it would’ve been something.

But with Gallinari not available because of rest with the Clippers on the second night of back-to-back games, they had to get it from someone else.

“We told our guys from day one, we’re not going to use all the excuses — youth, whatever,” coach Doc Rivers said before Tuesday’s game. “We’re just not going to use that.”

So, it was execution, not fatigue, that cost the Clippers in a 125-104 loss.

Gallinari, who also lightly twisted an ankle Monday against Boston, will be back in the Clippers’ next game.

In the same pregame news conference where Rivers said the Clippers weren’t going to make excuses, he also predicted that the team would have a tough time slowing down the Trail Blazers’ backcourt.

“As long as they have those two guards there, they’re going to do some winning. They’re very, very difficult to guard,” Rivers said. “If you put that plus the system that they’re in, it makes them very difficult to match up to. It just does.

“You know it’s coming. We just walked over it. And you know it’s going to be hard to stop.”

CJ McCollum, who started the game by missing his first seven shots, made an open three-point basket right before the halftime buzzer. Including that basket, McCollum proceeded to make 12 of his next 14 shots, including eight of nine in the fourth quarter.

“We made a lot of mistakes but CJ McCollum was on fire,” Rivers said.

McCollum scored 23 points in the fourth quarter; the Clippers managed 20 points in the final 12 minutes.

“What’s it like looking at that?” Lou Williams said. “It’s not a good time. But he’s a talented player. He’s done that before on numerous occasions, and unfortunately, one was tonight.”

McCollum’s barrage, paired with 20-point efforts from backcourt mate Lillard and from center Jusuf Nurkic wiped out a Clippers lead that grew to as many as eight points in the first half.

The Clippers, who started the game hot, led by rookie guard Shai Gilgeous-Alexander, never cooled down from three-point range, making 60% of those shots, but Portland limited the Clippers to only 15 tries.

Montrezl Harrell had 22 points and 11 rebounds, but they weren’t enough to hold up against McCollum and Portland.

“It was still a winnable game for us,” forward JaMychal Green said. “Obviously, [Gallinari] would’ve helped us. … We just didn’t lock down on defense.”

Clippers to add depth in backcourt

The Clippers intend to sign Justin Bibbs to a 10-day contract Wednesday, said a person not authorized to speak publicly.

The signing will put the Clippers roster at the 15-player maximum, which does not include two players on two-way contracts.

The 6-foot-5 guard has averaged 11.8 points, 3.0 rebounds and 2.7 assists for the G League’s Maine Red Claws this season, his first as a professional.

Bibbs averaged 13.3 points last season as a senior at Virginia Tech on 49% shooting overall and 40% shooting on three-pointers. He was undrafted but played with Boston during the summer league before being waived during training camp. He is expected to play with the Clippers’ G League affiliate in Ontario.

Etc.

Rivers said that forward Luc Mbah a Moute, signed this season to add versatility on defense, could sit out the rest of the season because of a sore knee. Mbah a Moute tried to return to practice last week and couldn’t make it through the workout. … The Clippers’ favorable late-season schedule continues with a day off Wednesday before returning to Staples Center on Friday against the Chicago Bulls.

Staff writer Andrew Greif contributed to this report.

dan.woike@latimes.com

Twitter @DanWoikeSports