Williams scored 22 points off the bench to give some help to one-man show Paul Millsap, rallying Atlanta to a 103-95 victory that denied the Philadelphia 76ers their first winning streak in nearly three months.
The Hawks, clinging to the final playoff spot in the East, snapped a six-game losing streak and won for only the seventh time in 27 games. They came into the night one game ahead of the New York Knicks.
"We all kind of looked at each other," said Hawks guard Kyle Korver, who returned to the lineup after missing six games with back spasms. "We all know what's on the line."
Williams sat out seven straight games in March, but it didn't have anything to do with being hurt. He was on the outs with first-year coach Mike Budenholzer, who didn't play his top bench scorer for seven straight games even though the Hawks were struggling mightily.
The message received, Williams' playing time has picked up over the last seven games. He came through with two crucial 3-pointers in the closing minutes as the Hawks bounced back from an early 14-point deficit.
"That's what we've been expecting from him all season," teammate DeMarre Carroll said. "Coach did a good job of not playing Lou, to show him that he couldn't take his opportunities for granted. He's playing some better basketball now."
Millsap carried the Hawks much of the night, also snagging a season-high 17 rebounds. But Williams hit the biggest shots down the stretch, a floater that snapped a 92-all tie, then back-to-back 3s from deep in the same corner to finish off the 76ers. It was his most points since a season-high 28 against Charlotte on Dec. 28.
"That was the first time I had to deal with that in my career," Williams said on his benching. "We weren't in a good rhythm and Coach wanted to change things up, try something new. He told me to stay ready. That's what I did."
The 76ers were coming off a victory over Detroit, snapping an NBA record-tying streak of 26 consecutive losses. But they couldn't win two in a row for the first time since Jan. 4.
If only the 76ers could have figured out a way to stop Williams.
"Lou did what Lou does -- came out and hit two big 3s, and the game pretty much was determined at that stage," 76ers coach Brett Brown said. "He went back to the old Lou."
The 76ers led from the opening minutes until late in the third, when the Hawks stormed to the front by closing the period on a 9-0 run. Williams got it going with a three-point play, Carroll dunked off a turnover, Williams made two more free throws, and Carroll laid one in to give Atlanta a 75-73 lead heading to the final quarter.
Philadelphia turned it over twice and missed its final four shots of the period, the last of those a reverse layup by Elliot Williams that rolled off the rim. Atlanta's Mike Scott stood defiantly over Williams after playing him tough, the 76ers player sprawled out beneath him on the floor.
The Hawks shot just 32 percent in the first half, were out front for a total of only 29 seconds, and trailed 53-43 at the break.
76ers F Arnett Moultrie was suspended five games without pay for a league drug violation. Moultrie, who played 12 games for Philadelphia this season, was assigned to Delaware of the D-League. He can't play with the minor league team during his suspension, either. "Arnett is still a part of the team and we will reach out to him and help him where we can," Brown said. ... Korver finished with 11 points on 3-of-10 shooting. ... Atlanta swept the season series, following up a 113-103 victory at home and a 125-99 win in Philadelphia that started the 76ers' historic losing streak.