Celtics Coach Ime Udoka was happy with the looks his team was able to get late in its game against the Bucks on Sunday, but they didn’t make enough of them and lost 117-113. Jon Durr/Associated Press

The shorthanded Celtics played one of their best games of the season through the first 42 minutes of action in Milwaukee on Christmas afternoon. Yet, the visitors had nothing to show for all that hard work after the buzzer sounded at Fiserv Forum: The Bucks used a 21-4 run over the final six minutes of regulation to escape with a 117-113 victory.

The late-game collapse by Boston has become a standard theme for this group early in the season, leading to a sub .500 start through 33 games. And that’s a trend that new head coach Ime Udoka wants to stop amid a pair of ugly finishes this week against a pair of Eastern Conference contenders.

“What I said to the group was, ‘We have to figure this out as a team, as a coaching staff, how to maintain these leads especially late in the games,’ ” Udoka said of his message in the locker room. “It gets a little frustrating and sometimes it’s as simple as making shots. Wes Matthews gets a kickout 3 and makes his. We get two or three wide-open 3 that were missed that obviously would have extended the lead or kept it. It’s sometimes as simple as that but the message is we’re very close.

“The game we felt we played well enough other than a stretch in the third quarter. Even with that, we still had chances to win it and had a turnover or two late and missed some wide open shots. It’s something we need to figure out obviously and the endings in a lot of these games, we feel like we’re giving them away. That can get a little frustrating for sure.”

Udoka is right to be frustrated after a closer look at the numbers. Boston is 6-12 in crunch-time situations this season according to NBA.com, (games within five points in the final five minutes) and that’s the second-worst record in the league this season among all 30 teams.

The Celtics are showing vulnerability on both sides of the ball in those scenarios, ranking 20th in both offensive and defensive efficiency in crunch time spots, which has led to late-game leads quickly dissipating. The Celtics failed to make a field goal in the final 6:11 of regulation against Milwaukee but Udoka was happy with the shots that his group was generating on Saturday late, despite the misses.

“I thought we got excellent shots,” Udoka said. “Jayson (Tatum) missed two wide open 3s, Marcus missed one, Jaylen Brown missed a solid pull-up. Offensively at the end, you get wide open looks and make them it’s a different story.”

The Celtics lack of reliable 3-point shooting certainly came back to haunt them in those moments as well as key pieces missing from the game due to the team’s COVID-19 outbreak. With defenses keying in on Tatum and Brown during crunch time and those guys struggling with their own shots in late-game isolation situations, there hasn’t been an easy method to get clean looks from reliable shooters.

“If we get wide open shots, that’s the point of what we’re running (on offense),” Udoka said of his playcalling. “(If) it was a favorable matchup, they were trying to double Jayson and he got off the ball, and then the guy has to make shots. Then he got downhill and we had some turnovers there. But the shot quality, what we got, was good at the end. We just didn’t make them.”

There is no easy solution here for Udoka and the Celtics but the biggest key is all parties need to be better to keep this pattern from spoiling the team’s season. Udoka and his coaching staff must get more creative with late-game play calls to avoid putting the ball in tough spots for Brown and Tatum and find ways to get the ball into the hands of better shooters. Those All-Stars also need to start executing better to get to the rim instead of giving up costly turnovers that lead to easy transition opportunities.

A lot of the attention will be on the shorthanded personnel the Celtics had for the defeat but this is an issue that goes back multiple seasons for Boston. Until something changes in crunch time, this looks like a group that will remain a sharp tier below contenders in the Eastern Conference.