Doc Rivers says he is not concerned, but he also isn’t dismissing the 76ers’ recent defensive effort. While the coach claimed his team didn’t have the needed focus and paid for it Thursday night during a 122-109 loss to a depleted Brooklyn Nets team, it marked the second straight poor defensive effort.

This was the second game of a back-to-back, and the Sixers looked fatigued. But they weren’t exactly dominating on defense on the front end, either.

The night before, the Sixers got away with a poor performance on D when they outscored the Washington Wizards, 141-136, despite Bradley Beal’s 60 points.

“I’m not that concerned. I love our defensive wall,” Rivers said after the loss in Brooklyn dropped the Sixers to 7-2. “I thought [Wednesday vs. Washington] in the first half, we were terrific, got a big lead and let up. And then it carried over tonight, so a lot of fixable things. Not that concerned with it, to be honest.”

Actually, the defense wasn’t exactly in lockdown mode in the first half against Washington. The Wizards scored 67 points and shot 51.1% from the field, including 8-for18 (44.4%) from three-point range.

The only reason it didn’t seem as bad is that the Wizards totally abandoned playing defense, allowing 82 first-half points.

In the second half, Washington shot 49% from the field, including 8-for-19 (42.9%) from beyond the arc.

The Sixers entered the Nets game with the NBA’s best defensive rating (102.7), meaning they were allowing that many points per 100 possessions.

“The ‘best’ defensive team just gave up [nearly] 125 points to a team without Kyrie and KD,” TNT analyst and Sixers great Charles Barkley said afterward.

Barkley was referring to the fact that the Nets were without their superstar duo of Kevin Durant and Kyrie Irving. Durant was out because of contact tracing/exposure to COVID-19. Irving missed the game for personal reasons.

The Nets also were without explosive guard Spencer Dinwiddie, who has a partially torn ACL.

Still, Brooklyn was effective from three-point range, shooting 15-for-37 (40.5%). The Sixers had an especially difficult time containing Joe Harris, among the NBA’s top perimeter threats. Harris had 28 points off the bench, hitting 6-of-9 three-pointers.

Shake Milton, who started in place of Seth Curry (left ankle soreness) and scored a team-high 24 points, said the Sixers have to pay attention to detail on defense, something that hasn’t happened the last two games.

“We’ve got to tighten up, and things that would be easier if you had practice time. But you don’t, so you kind of have to learn on the fly,” Milton said.

As for Curry, The Inquirer confirmed a report after the game by ESPN that he had tested positive for the coronavirus.

Brooklyn’s Caris LeVert continually got to the rim en route to 22 points Thursday, and also had 10 assists. What helped the Sixers even stay remotely in the game was LeVert’s poor shooting. He was 9-for-25 from the field and 4-for-10 from the foul line.

The Sixers’ Danny Green says it’s too early to be worried about the defense, but ...

“We are not concerned. We are not worried, but it is something that we want to clean up, nip in the bud and try to grasp and learn as quickly as we possibly can to get better at,” Green said. “The sooner the better, because that is what we are going to hang our hats on.”