Horford was ruled inactive just before the game due to a back bruise suffered the day before. His absence was barely felt, as Smith dominated inside.
"We were shorter offensively, but Smoove picked up the slack and had an unbelievable game," said Joe Johnson, who scored 21 for the Hawks. "You can tell, he took an approach he wanted to get everything that came off the glass."
Smith said he didn't feel any extra pressure to make up for the loss of Horford.
"We have so many weapons on the team, it can be anybody's night at any given time," Smith said. "Coach was running plays for me and I was able to execute."
Atlanta has now won the last 12 meetings between the teams. Washington hasn't beaten the Hawks since an overtime win in Atlanta on Jan. 11, 2008.
"I've been on the other end," Wizards coach Flip Saunders said. "It becomes very psychological. I wasn't even aware of it. I don't think usually what happens in previous years has a lot to do with what happens this year. It's good ink to write about."
The loss also extended Washington's losing streak to eight, a season high.
Marvin Williams scored 15 points and had 12 rebounds -- his second double-double this season -- for Atlanta, which has won three in a row.
Atlanta led the entire first half, building the lead to 13 early in the second quarter. The Hawks were up 52-46 at the half before the Wizards clawed back.
Washington briefly took the lead late in the third quarter before the Hawks closed the period on a 12-4 run, the final six scored by Jamal Crawford, and Atlanta never relinquished the lead in the fourth quarter.
"Even when they took the lead, I still felt very comfortable," Atlanta coach Larry Drew said. "I still felt we were in great position. I knew our guys were not going to panic."
The last serious threat from the Wizards came when Kirk Hinrich's 3-pointer drew Washington within three points, 80-77, with eight minutes to play. Atlanta held Washington scoreless for the next three minutes as the Hawks scored six straight points, including a dunk by Damien Wilkins, to take full control of the game.
"We knew they were going to make a run," Johnson said, "but we knew also we had a chance to counter that and make one of our own and we did that in the fourth quarter."
Washington's star rookie point guard John Wall scored 18 points but was 2 of 7 from the free throw line, part of an 8 for 18 team mark on free throws. He also had a scary moment in the third quarter, when Jason Collins fell on his left ankle in a tangle for a loose ball. Wall briefly stayed on the ground, clutching his ankle with a grimace. He was tended to by trainers during a timeout but remained in the game.
"It was a rough game," said JaVale McGee, who scored 12. "We were out there trying to play hard and take care of home. They came out scoring and making baskets and we didn't make our free throws, so it messed us up."
While Horford has earned All-Star bids each of the last two seasons, Smith has been left off despite having credentials for consideration.
"He's really rounded his game," Drew said. "Certainly there's an argument he should have made the All-Star team."
After the game, Smith was asked if his performance made a case for him to be looked at as an All-Star alternate if needed.
"If it happens, it happens," he said. "If not, I'll spend my time resting my body and spend time with my family."
Horford's injury came Friday, when he had a hard fall after a flagrant foul by the Clippers' Blake Griffin. Horford made two free throws in the final second of Atlanta's 101-100 win, but Drew said he was still sore Saturday. ... Washington F Yi Jianlian left the game in the fourth quarter with a sprained left ankle. Yi jumped to defend a shot and his leg buckled after his ankle landed awkwardly on Wall's foot. Yi stayed on the ground before being helped to the locker room and did not return. ... The Wizards' losing streak is their longest since a 16-game skid last March. ... Atlanta is 12-4 in the second game when playing back-to-back this season.