Nikola Vucevic would like to be able to do more to help the Chicago Bulls amid their coronavirus outbreak but has no explanation for his shooting woes.

The Bulls lost two more players to health and safety protocols ahead of Saturday's defeat to the Miami Heat, meaning they now have seven players out due to COVID-19.

Among them is DeMar DeRozan, whose team-high 26.4 points per game this season have helped transform Chicago into contenders in the East.

Two-time All-Star Vucevic missed seven games earlier in the year after returning a positive test, although his below-par displays so far in 2021-22 mean the former Orlando Magic center was not quite such a big miss.

Through the first three weeks of the season before his lay-off, Vucevic shot 39.5 per cent from the field and averaged 13.6 points.

There has been slight improvement since the 31-year-old's return, shooting 41.3 per cent and scoring 17.0 points, boosted by a 30-point game against the Charlotte Hornets, but his marks for the season (40.4 per cent shooting, 15.2 points per game) remain well down on 2020-21 (47.7 per cent, 23.4).

Among players to play in 70 per cent of team games, only Jonas Valanciunas (59.2 to 51.7) has suffered a larger decline in field-goal shooting percentage from this season to last, while Bradley Beal (31.3 to 22.5) is the sole NBA star to see a greater drop-off in points output.

The 118-92 loss to the Heat saw Vucevic's worst shooting game of the season, making just three of 15 attempts from the field (20.0 per cent) for 10 points.

"I don't really have an explanation for what's going on with my shot," the 49.3-per-cent career shooter said afterwards.

"It's something I was always very consistent with, really good throughout my whole career, around a 50-per-cent shooter, so I don't know."

The Bulls' overall improvement – now 17-10 after last year's 31-41 record, representing the league's third-largest increase in winning percentage – had largely hidden Vucevic's poor form until now.

"It's tough when you want to go out there, play well and help the team win," he said. "You want to do your job. It's obviously frustrating.

"I have a lot of pride in myself and put in the work and everything, but it's just not working for me right now.

"I've never been through a slump like this, and I just have to work myself out of it. There's no other way.

"Obviously I'm not playing well right now, I'm not doing what I'm supposed to do, not doing my job, and I've just got to figure it out – it's plain and simple."

He added: "There are games where maybe I didn't play as well, but we were winning and it's not that big of a deal.

"When you lose and you don't play well, you feel like it's even more of your responsibility, your fault."

Coach Billy Donovan has sympathy for his players amid the uncertainty around the team, although he wants more from Vucevic.

"Everybody's probably a little bit out of sorts right now, just because we keep losing players and we're throwing different guys in and need more from different guys," he said.

The coach at least knows Vucevic's performances are not for a lack of effort.

"With some of the scoring that's missing from our team, we're going to need him and Lonzo to pick up the slack in different ways," Donovan added.

"I thought he had some pretty decent looks. But I trust him and believe in him – maybe I wouldn't feel that way if I didn't see him working."