CHICAGO – This was one of the games that could ultimately determine the 76ers' postseason fate.

A lot of attention is being paid to their home-and-home matchups against the Toronto Raptors on Thursday at the Wells Fargo Center and Saturday at Air Canada Centre.  There's also a buzz surrounding the team's Christmas Day game against the New York Knicks at Madison Square Garden.

While those games against playoff-caliber opponents spark water-cooler conversations, the Sixers need to beat the league's cellar-dwellers.

They failed to do that Monday night against the suddenly hot Chicago Bulls. Sparked by a 13-0 fourth-quarter run, the Bulls prevailed, 117-115, here at the United Center.

The Sixers did have a chance to tie the score in the closing seconds. However, Ben Simmons drove the lane and missed a layup with 2.6 seconds left.

Bulls reserve forward Nikola Mirotic grabbed the defensive rebound and was fouled with 0.4 seconds remaining. He went on to miss both foul shots. Simmons grabbed the defensive rebound and misfired on a desperation heave at the buzzer.

"I knew I was going to take a shot," Simmons said of his missed layup. "Try to get to the rim or draw a foul. It's hard to get a foul in the final quarter in a game like that. You know refs are going to call anything like that.

"It was a chance to win, but it didn't happen."

The loss dropped the Sixers to 14-15. They have lost two straight and six of their last seven games.  Meanwhile, Chicago (9-20) extended its winning streak to six games.

Some may attribute this loss to being undermanned against a team on a roll.  The Sixers were at a disadvantage without two of their top seven players in Joel Embiid and Trevor Booker.

However, others will look at this as just another loss to a bad team, record-wise. In their eyes, this setback is no different than losing to subpar teams that they were expected to beat — the Sacramento Kings (Nov. 9), the Phoenix Suns (Dec. 4), and the Los Angeles Lakers (Dec. 7).

The Sixers will get to avenge their 109-108 November road loss to the Kings (9-20) when the squads meet Tuesday night at the Wells Fargo Center.

"We got to win tomorrow," said Simmons, whose squad has also lost five straight games to teams that came into the matchup with .500 records or worse. "Back to backs, it's going to be tough. … Sacramento is a good young team. But Obviously I think we're good."

Dario Saric led the Sixers with 27 points. Twenty of his points came after intermission. Simmons finished with 19 points, 12 rebounds, nine assists and four blocks for his 17th double-double.

Former Sixer Justin Holiday had 20 points. However, all of his damage was done in the first half.  He failed to score after intermission and missed both of his shot attempts.

But he didn't need to. Kris Dunn and  Mirotic took up the slack in the fourth quarter.

Dunn scored seven of his 22 points in the final quarter. Meanwhile, six of Mirotic's 22 points came in the fourth.

The Sixers had a 101-94 lead after Simmons' layup with 6 minutes, 49 seconds remaining.  Then after the Bulls' David Nwaba hit a pair of foul shots, Jerryd Bayless converted a four-point play to put the Sixers up nine (105-96) with 5:51 remaining.

The Bulls responded with a 16-2 run to take a 112-107 lead on Kris Dunn's basket with 1:26 left. Those two points capped 13 straight by Chicago.

The Sixers pulled within two points (117-115) on a three-pointer by Saric with 39.3 seconds left. Mirotic missed on the ensuing possession, setting up Simmons with a chance to knot the score with 2.6 seconds left.

But the Sixers could have used Booker and Embiid.

Booker will also miss Tuesday's game with a sprained left ankle. Meanwhile, Embiid was sidelined for rest, part of what the Sixers term "load management." As a result, he doesn't play on consecutive nights.

The team's franchise player is dealing with back tightness and is recovering from left knee surgery in March. He didn't play on consecutive nights last season because of his right foot. Embiid had two foot operations, preventing him from playing in the 2014-15 and 2015-16 seasons.

The Sixers changed their style of play without their big man.

Embiid commands a lot of attention. As the best player on the team, the Sixers must find a way to equally feed him the ball while also playing at an up-tempo pace.

"Amir is the guy that can do a lot of different things as well," Robert Covington said. "He does it in difference ways. So it's a different approach. But it allows us as a team to get up and down a lot more."

A solid role player, Johnson (four points, two rebounds) helps the Sixers' guards by constantly setting screens and focusing on grabbing rebounds.

However, the Sixers would have benefited from mixing things up by feeding Embiid on the block.  That's because the Bulls took advantage of the up-tempo style of play.

Monday's game was a homecoming for Sixers and Chicago-area natives  Covington (10 points), Richaun Holmes (14 points) and Jacob Pullen.