By Cody Westerlund–

CHICAGO (CBS) — Amid a strong 4-2 road trip recently, a weakness of the Bulls was largely masked amid the good vibes and general success.

That vulnerability revealed itself Wednesday night.

In a 96-90 loss to the Lakers at the United Center, the Bulls saw their bench get outplayed again, this time in spectacular fashion. The five Chicago reserves who saw action — Nikola Mirotic, Isaiah Canaan, Denzel Valentine, Bobby Portis and Jerian Grant — combined to score 16 points on 7-of-25 shooting on a night Los Angeles’ bench scored 56 points. Most noticeably, the bench played the leading role in the Bulls squandering a 14-point lead late in the first quarter.

That continued a recent trend that’s seen Chicago bleed points late in first quarters and/or early in second quarters when the reserves take over. In a recent loss at Denver, the Bulls’ second unit was the primary culprit in a 24-0 run by the Nuggets. Even in a blowout win at Philadelphia last Friday, the lone slump of significance for Chicago came with a reserve-laden group in early.

So there’s reason for worry, even if the Bulls (10-7) won’t admit it.

“Nope, not at all,” Jimmy Butler said when asked if the starters felt an extra burden. “This is a team. They’re going to go through slumps, we’re going to go through slumps. And that’s fine. We just have to find ways to win games, whether our bench is outscoring everybody or whatever it may be. We got to figure out a way to win.”

Added Dwyane Wade: “No, we’re fine. We have enough. We just got to win games like this.”

The bench’s recent struggles have come with two key players out for long stretches. Guard Michael Carter-Williams hasn’t played since Oct. 31, when he suffered a bone bruise in his knee and a bone chip in his left wrist that’s still plaguing him. Forward Doug McDermott — the team’s de facto sixth man — has also now missed seven straight games with a concussion, his second of the season.

So reinforcements could be on the way in a few more weeks. The catch is, Carter-Williams and McDermott may not be suited to fix perhaps the biggest issue: the second unit’s rim protection. When coach Fred Hoiberg has paired big men Bobby Portis and Nikola Mirotic together, the results have usually ranged from poor to disastrous, with opponents constantly getting favorable looks on forays to the hoop.

Entering Tuesday’s game, the two most-used five-man Bulls units that were anchored by the Portis-Mirotic pairing down low had defensive ratings of 111.9 and 145.4. The Lakers then went out and exploited that weakness, outscoring the Bulls, 19-7, in the approximately 5 1/2 minutes Portis and Mirotic played together Wednesday.

Hoiberg has tinkered a bit lately — notably taking Taj Gibson out earlier in the first quarter and getting him in sooner in the second — but disaster has struck so swiftly that the minor adjustments have mattered little. And Hoiberg has been unwilling to turn to big man Cristiano Felicio, a more nimble defender than Portis, who the organization has more of an investment in after taking him in the first round of the 2015 draft.

“I’ve tried to get a couple starters out a little earlier and get them back in there with our second unit,” Hoiberg said. “Again, we’ve gotten some solid minutes from the bench in this early portion of the season. Tonight, obviously we struggled in that area – keep battling, keep fighting.”

In such a team game, there’s more context to this than just the Portis-Mirotic pairing. But with Wade preferring the mid-quarter breaks, his minutes management plan going well and Butler traditionally playing the entire first quarter, the easiest change would seem to come in the big man rotation, not in the backcourt.

For now, as they could directly trace their last two losses to poor bench play, the Bulls are refusing to acknowledge that line of thinking.

“Like I tell everybody each and every day, just do what you do best, just play hard and everything will fall into line, will fall into place,” Butler said. “They’re still getting their rhythm, which is fine. I just want those guys to stay confident, because we need them. It’s a long season, and they’re on this team for a reason.”

Cody Westerlund is a sports editor for CBSChicago.com and covers the Bulls. He’s also the co-host of the @LockedOnBulls podcast, which you can subscribe to on iTunes and Stitcher. Follow him on Twitter @CodyWesterlund.