Bulls guard Josh Giddey sat alone in the last seat on the bench Friday. All he could do, aside from brief moments when he squeezed his head in frustration, was stare at the floor.

A white towel wrapped around his neck, Giddey was as down as he has been all season.

With 8:51 left in the fourth quarter, the game was over. The Heat were ahead by 30 points in a game they dominated from the second quarter on and won 143-107.

It wasn’t a banner night for Giddey, even though he finished with 19 points, 11 rebounds and nine assists. He shot only 6-for-14 from the field and committed three turnovers.

Despite the Bulls revamping their offensive scheme and vowing to commit to defense and rebounding, they still didn’t measure up to the Heat, who ran their offense flawlessly and benefitted from the Bulls’ incessant fouling, shooting 44 free throws.

‘‘We’ve got to start to be the aggressor,’’ Giddey said. ‘‘Teams are starting to realize they can punish us on the offensive boards, and they’re starting to run through us.’’

The franchises have been linked for the last couple of seasons, with both residing in the NBA middle — that is, not good enough to contend but better than teams who are tanking. And as has been the case in those seasons, the Heat showed they have the Bulls’ number. Whatever level the Bulls think they’re at, the Heat are a step above.

Not much went right for the Bulls after a competitive first quarter. They missed shots short, fumbled passes and showed little defensive resistance.

The second quarter was ghastly. The Bulls allowed the Heat to take control and open an 18-point halftime lead. They missed free throws, committed sloppy turnovers and let the Heat dominate them physically.

‘‘I enjoy competing against them because I think you find out more about your team doing that,’’ head coach Billy Donovan said.

The Bulls have to do a better job of boxing out and keeping opposing teams off the offensive glass. When they’re not grabbing rebounds, it keeps them from getting out in transition. Teams have taken advantage of the Bulls’ lack of size and are sending all five players to the offensive glass.

‘‘NBA players are too talented [for us] to be bad at the small things,’’ Giddey said. ‘‘Guys are just driving downhill. Personnel is getting thrown out the windows. So we’ve got to be better in that area, and that’s everybody. We’ve got to make players play against multiple bodies instead of leaving guys on the island one-on-one.’’

In the second quarter, the Bulls were searching for answers defensively. Donovan turned to a 3-2 zone, but the Heat promptly worked the ball around before finding 7-1 Kel’el Ware under the basket for a lob. There wasn’t much resistance from the Bulls, as the Heat were able to get to their spots whenever they wanted.

Offensively, the Heat bludgeoned the Bulls with their size in the paint. Defensively, they stifled the Bulls’ high-octane attack and kept the United Center quiet.

The Bulls already were looking to turn the page after the loss.

‘‘It’s a good thing we’ve got another game in 24 hours,’’ Giddey said. ‘‘We get another shot at Washington [on Saturday night].’’