The 34-year-old Williams learned of the assignment at the same time he was told that star teammate Trae Young would sit out Game 4 with a foot injury.
But Williams was more than up to the task and contributed 21 points and eight assists as Atlanta posted a 110-88 victory over the visiting Milwaukee Bucks on Tuesday night to even the Eastern Conference finals at two games apiece.
Williams’ big effort fueled the fifth-seeded Hawks on a night in which the third-seeded Bucks lost their own star.
Two-time NBA MVP Giannis Antetokounmpo hyperextended his left knee in the third quarter and didn’t return. His status for Thursday’s Game 5 in Milwaukee is unclear.
“We’ll see how he is tomorrow,” Bucks coach Mike Budenholzer said afterward. “We’ll take everything as it comes. We’ll evaluate it. We’ve got a heck of a team, a heck of a roster.”
Young sustained a bone bruise in his right foot during Game 3 on Sunday night when he inadvertently stepped on an official’s foot.
Hawks coach Nate McMillan said Young will be a game-time decision for Game 5.
As Young cheered from the bench, Williams ran the team expertly by committing just one turnover in 35 minutes. He made 7 of 9 field-goal attempts.
“I was just staying poised,” said Williams, a three-time NBA Sixth Man of the Year recipient. “I just had to refocus my energy and put on a different hat and get ready for the game.
“It was just one of those nights. Everybody played with confidence, everybody played at a high level. So going back to Milwaukee tomorrow, we’re going to bottle it up and take it with us.”
Teammate Bogdan Bogdanovic made six 3-pointers while adding 20 points for the Hawks, who never trailed and led by as many as 25 points.
Jrue Holiday recorded 19 points and nine assists and Khris Middleton had 16 points and eight rebounds for the Bucks, who were a woeful 8 of 39 (20.5 percent) from 3-point range while shooting 39.3 percent overall. Middleton was just 6-of-17 shooting after erupting for 38 points in Milwaukee’s Game 3 win.
Antetokounmpo had 14 points and eight rebounds in 24 minutes before exiting with 7:14 left in the third period.
Antetokounmpo was helped off the floor by his brother Thanasis after getting hurt.
Antetokounmpo got injured when he leaped to defend an alley-oop pass to Hawks big man Clint Capela. Antetokounmpo hyperextended his knee as he landed. He fell to the court in intense pain, grabbing the knee, and Capela fell on top of him after scoring the basket.
Capela’s basket on the play in which Antetokounmpo was hurt ignited a 17-2 burst that saw the Hawks open up a 77-54 lead with 3:18 left in the third. Bogdanovic knocked down three 3-pointers during the run.
Cam Reddish’s 3-pointer with 29.7 seconds left elevated Atlanta’s lead to 87-62 entering the fourth quarter.
Reddish and Kevin Huerter buried baskets 13 seconds apart in the final stanza to make it 104-80 with 4:20 left, prompting Budenholzer to pull Holiday and Middleton and look toward Game 5.
Capela added 15 points for the Hawks before leaving with 3:28 left in the fourth after taking an elbow to his nose from Milwaukee’s Sam Merrill. Huerter scored 15, Reddish added 12 and Danilo Gallinari tallied 10 for Atlanta, which shot 50 percent from the field and was 13 of 38 (34.2 percent) from behind the arc.
“Lou did an excellent job for us tonight running the team, establishing tempo,” McMillan said. “We got great ball movement tonight. All the things we needed, we got that tonight.”
Williams hit all four of his first-half field-goal attempts — including one 3-pointer — while scoring 13 points to help the Hawks hold a 51-38 halftime lead.
–Field Level Media