Damian Lillard acknowledged the Milwaukee Bucks must replace Giannis Antetokounmpo "by committee" when he is out, after he sat out Tuesday's win over the Miami Heat.

Former NBA MVP Antetokounmpo was a pre-game scratch on Tuesday, having suffered from swelling in his left knee during the warmups.

However, Lillard had 37 points and 12 assists as Milwaukee registered a 106-103 victory in a topsy-turvy NBA Cup game.

The Bucks squandered a 22-point second-half lead before two late AJ Green 3-pointers got them over the line, improving them to 3-0 in NBA Cup play this campaign.

Coach Doc Rivers was unable to offer an update on Antetokounmpo's condition after the game, with the Bucks now not in action until they host the Washington Wizards on Saturday.

"Giannis doesn't miss many games," Rivers said. "Whatever it is, I'm sure it was the right thing to do."

Antetokounmpo is averaging a career-high 32.4 points on 60.8% shooting so far this season, to go with 11.9 rebounds and 6.4 assists per game.

The Bucks lost the only other game Antetokounmpo has missed this season – versus the Cleveland Cavaliers on November 4.

Though he took up the mantle with a fine display on Tuesday, Lillard said it will always be a team effort for Milwaukee without their star player.

"It's always going to be done by committee," Lillard said of replacing Antetokounmpo.

"Everybody is going to have to do a little bit more with such a hole in our lineup, but I know guys are going to look to me to step up."

The Bucks are now 9-9 for the season after making a dismal 2-8 start, and Lillard believes things are starting to come together for the team.

"It's not something we're looking at it and celebrating, but it's the fact that we're going in the right direction by the way we're playing," he said of their improved run.

"We're beating good teams. We're winning at home. We're winning on the road, a game like tonight, without Giannis.

"The way we're doing it is sustainable, and it's showing that we're doing what we wanted to be doing coming into the season."