CHICAGO - There have been so many instances to define this horrible 76ers season, such as losing nine games in which they had a fourth-quarter lead and being embarrassed in a 51-point home loss to the San Antonio Spurs.

Few may be as eye-opening, or frustrating, as Monday night's second and third quarters against the Chicago Bulls.

In the second quarter at the United Center, the Sixers might have put forth their best 12 minutes of the season. They made 16 of 25 shots, with 10 of those baskets coming on assists, and scored 37 points to take a 56-51 halftime advantage.

How different were they in the third? Imagine Donald Trump coming out for Tuesday's debate with a crewcut and a passive-aggressive attitude. The Sixers were almost unrecognizable from the previous quarter as they were outscored by 34-12, allowing Chicago to end the quarter with a 14-0 run. That spurt grew to 26-1 in the fourth as the Sixers saw any chance of garnering their second win of the season fly away, like so many of their passes this season.

The final was 115-96. You have to wonder what the home office in Phoenix is thinking.

"We're getting better offensively, starting to execute better and doing what the coaches want from us," said Jahlil Okafor, who returned to his hometown and scored 22 points to go with eight rebounds. "But then we got stagnant in our offense and stopped executing."

That is a little bit of an understatement.

"We had a good second period. We knew they would come out of the locker room like they did," said Brett Brown, whose team fell to 1-25. "You get stood up and we can't execute. Basic stuff. We had two turnovers in the first half and seven in the third period.

"They have to learn how to get through that. You see the great and then you see the really poor. You saw that in two successive periods. In the second, we had pace and we executed and no turnovers. Then you saw a third period where it gets to be real NBA basketball and we get stood up. And we weren't able to execute."

It's surprising the coach didn't have the bends after going from such a high point to such a low one so fast. It's as if a switch is turned on, the opponent shows just a little bit more energy and a positive game becomes a negative one in a matter of minutes.

Robert Covington scored 15 and Tony Wroten 12 to back Okafor. Jimmy Butler's 23 led five players in double figures for the Bulls (14-8).

"You have to challenge each other and keep it real," Brown said. "We need to respond when we get punched and right now we don't. They fight most times, but that third period was very revealing.

"I haven't seen that vast of a canyon between two periods. On one level, you say in the second period we were purposeful in our offense. Then you see the complete 'how do we handle this' mentality."

Again, the answer is, not very well.

Familiar face sidelined

If you're a fan of the NBA, you know more than just the teams, players and coaches. And if you are familiar with the referees, there is no one more recognizable than Joey Crawford.

But Crawford hasn't been running the court of late after suffering a knee injury early in the season. He had surgery a couple of weeks ago, performed by Dr. Jack McPhilemy, and is recovering at his Newtown Square home, though he'll be stopping in the NBA offices as a replay official a few times during the holidays.

An NBA referee since 1977, Crawford says he is just about 60 games away from breaking the record of most games officiated, set by the recently retired Dick Bavetta. He will begin rehab sometime after New Year's Day, but he knows a return is not guaranteed.

"The knee is not good," said Crawford, 64. "There's arthritis, not much cartilage and the meniscus was torn. I hurt it last season, was out for a couple of months, came back and finished things out. I rehabbed during the offseason but it went out again.

"I don't know if I'll be able to come back, we'll just have to see what happens. But if I can't, I'm happy. I've had a great run."

Crawford has overseen 313 playoff games and 50 NBA Finals games, both records. His father, Shag, and brother, Jerry, were longtime major league baseball umpires.

On Twitter: @BobCooney76