"It went all right," Favors said. "But we lost."
Millsap missed only the 14th game of his career because of injury after suffering a sprained ankle in the first half of Monday's 110-107 overtime loss against Boston.
He continued to play. But he could not practice Tuesday and did not participate in the Wednesday morning shootaround.
That's when Favors first learned he might be making his 16th start in parts of three seasons as a member of the Jazz.
"I really didn't find out for sure until before the game," Favors said. "Coach pulled me aside and told me. ... I just wanted to come out and rebound. Just play my game and rebound."
According to Corbin, the loss of Millsap hurt the Jazz against the Hawks.
"Paul is a big part of what we do here," he said. "I thought Derrick played well, but we missed his experience. ... He does more things than score."
At the same time, Corbin was quick to compliment Favors, who played 38 minutes.
It was the second-most minutes he has played this season and only the third time in Utah's 58 games he played more than 30.
"I thought he did a good job," Corbin said. "I thought he was aggressive on the defense end. He made some great defensive plays for us. He also got the ball on the post and made some good moves there. He got a little tired, but we're short-handed. So I thought he did a good job."
Favors got going early against the Hawks, even though he tried to scale back his aggressiveness to avoid foul trouble.
He had five points and five rebounds in the first nine minutes to help keep Utah close.
By halftime, Favors had 10 points and nine rebounds. But like the rest of the Jazz, he struggled in the third quarter, when he went scoreless and picked up three fouls in 5:10.
Still, the Jazz battled back from an 80-60 deficit. It was 90-82 with 4:48 left when Favors dumped the ball to Al Jefferson with a perfectly timed pass.
Jefferson's layup would have made it a six-point game, but Al Horford blocked the shot from behind and stalled Utah's comeback.
Corbin called Horford's block "... huge. A back-door play, and I thought Derrick made a nice pass. ... It was a big block for them."