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PHOENIX — Several things were apparent before Friday night’s 99-93 loss to the Suns.

The Bulls stayed stuck on their 12-3 record using their regular starters as Mike Dunleavy missed his 16th straight game. The up-and-down nature of this season continued with an inspired early effort and subsequent failed rally against an above-.500 team, coming, of course, on the heels of another disappointing loss to a sub-.500 team.

And players are reaching their breaking point about the oft-broken defense.

“We can score so many points now that we think we don’t have to guard anybody,” freshly-anointed All-Star Jimmy Butler said. “And that’s not the case. It hasn’t been working for us. It’s not going to work for us. So we need to stop doing that.

“We talk about it all the time. But it’s enough of the talk. Guys can rah-rah-rah and say we have to start playing defense. We’ve heard it for 40-some games now. One of these days, we’re going to get tired of getting our ass kicked and decide to play defense.”

The Suns certainly posed a challenge, entering ranked second behind the Warriors at 107.3 points per game.

The Bulls entered Friday ranked 18th in points-per-game allowed and ninth in opponents’ field-goal percentage. Since Tom Thibodeau arrived in 2010, the Bulls never have finished lower than third in the former and finished first or second three out of four times in the latter.

These are the defensive standards the Bulls are accustomed to meeting.

“We’re not guarding anybody right now,” Butler said. “That’s what you think when you think Chicago — how great we are on defense. We haven’t been that team but maybe three, four, five, six times this year tops. We can score so sometimes we can outscore teams. But we haven’t been playing any defense lately.”

Getting everybody healthy and solidifying the rotation will help. But the Bulls also have added offensive-minded players, have one rookie in the rotation in Nikola Mirotic and have struggled to guard pick-and-roll all season.

Too often, Derrick Rose has been caught up in screens. And with the less-mobile Pau Gasol at center, teams are getting more direct lines to the basket.

“We have to get better,” Thibodeau said. “We can’t pick and choose when we’re going to play defense.”

The Bulls’ vastly improved offense has increased pace, so allowing at least some more points is inevitable. But it’s the Bulls’ inability to get stops at critical times that has looked so unfamiliar.

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Again, Thibodeau pointed to some unfamiliar lineups.

“We have to get people healthy,” Thibodeau said. “But (starters out) is our reality. We have to figure that out. We have to find a way to get it done no matter who we have. Right now, it’s the moving parts that’s hard. Usually when you have a guy out, you know he’s out for whatever amount of time and you can build around that. Now, one game it’s this guy, the next game it’s another guy. That’s what we have to manage better.”

Layups: Dunleavy, who jammed ligaments in his right ankle Jan. 1, missed the rest of the month, sitting for the 16th straight time. “He feels like he’s close but he can’t get over that final hump to get out there,” Thibodeau said. The Bulls have four days off until their next game, on the road Feb. 4 against the Rockets. … Gasol’s career-high for double-doubles in a season is 43. He entered Friday with a league-best 29. … The Bulls stayed overnight in the Super Bowl host city before they were to fly to Chicago on Saturday morning for an off day.

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