Butler was touched on the right elbow by Marcus Smart on a turnaround jumper as the horn sounded, drawing a foul.
The Bulls' leading scorer stepped to the free-throw line and drilled both foul shots, making him nine-for-nine for the game and giving him 29 points.
"It was a big letdown", added Smart, who stripped Butler earlier in the final minute to keep the Celtics ahead at the time.
Covington left the game in the fourth quarter after hitting his head at or near the Boston bench diving for a loose ball.
Brad Stevens was livid about foul call on Marcus Smart
Thomas also fouled Jerian Grant down the other end, and the Bulls guard hit twice, cutting the Celtics' lead to a point. With the chip firmly on their shoulder, look for another hard fought game from the Sixers in Boston tonight.
In fact, coach Fred Hoiberg chalks up the recent up-and-down play to up-and-down health, which featured the Bulls not having Dwyane Wade for a third straight game.
Butler isolated against Marcus Smart on the left side of the court as the final seconds ticked off the clock.
Whether or not there was contact, it probably wasn't close enough to make that call. "We get up for the challenge", Gibson said. The Butler-Thomas matchup was terrific theatre down the stretch, as Thomas scored 11 fourth-quarter points on 3-of-8 shooting while Butler had a crucial block on him with 1:10 left.
Tinder acquires a Snapchat-like video app, Wheel
Wheel was created to "lower the barrier for entry to content creation" and to "make connection more comfortable", said Boukadakis. Tinder's acquisition of collaborative video app Wheel could mean video capability will be integrated in the near future.
Hoiberg, who has National Basketball Association experience as player, coach and in the front office, said before Thursday's game he does his best to ignore the rumor mill when it comes to the upcoming trade deadline. Smart has not only started to distinguish himself with improved point guard play but has helped fill the void left by Evan Turner's departure this summer.
"It's what he wants". One year later, the disenfranchised Rondo was traded away to Dallas and the Celtics haven't looked back. He's a guy that's going to go out and take the challenge, anything that is given to him.
Bulls: Host the Phoenix Suns next Friday night.
The C's have won 11 of 12 and sit just 2.5 games back of the Cleveland Cavaliers for the top spot in the Eastern Conference.
Journalism Awards for NASCAR-Daytona International Speedway news coverage by Henry Frederick
NASCAR has set the stage lengths for races this season, part of a radical revamp designed in hopes of making every lap matter. When the third stage concludes the first-place driver is declared the victor and points are distributed throughout the field.
As for the Bulls, Hoiberg was pleased his team was able to enter the All-Star break with a pair of wins in hand. And barring a blockbuster deal that sends Butler to the team he tormented for 40 minutes on Thursday, the Bulls will have that player as they continue their push toward.500 and a postseason berth. Moving forward we can't worry about who we're beating.