New England is about to find out if Jim Montgomery and Joe Mazzulla can actually coach.

They’ve passed every test so far. Both have proven they can manage success and that shouldn’t be overlooked. But both the Celtics and Bruins have hit turbulence with less than a month left in the regular season. They each started the week with losses to last-place teams — the Rockets and Blackhawks — that were a combined 39-90-6. Those were respective low points in tough recent stretches for both teams. Montgomery and Mazzulla have some important work to do.

Montgomery, whose system has been a perfect match for this Bruins roster, has a lot more cushion to work with. His Bruins have lost three of their last four games. Their pursuit of history has taken a hit, but they’re so far ahead in the Eastern Conference that they’ve got room and time to regroup before there are tangible consequences.

But the Bruins don’t want to be another Presidents’ Trophy winner that doesn’t win a Stanley Cup. Before losing games to Detroit (seventh place in the Atlantic) and Chicago, Montgomery’s challenge was going to be keeping his team sharp while still resting key players so the Bruins could enter the playoffs energized and ready for a deep run.

Now he needs to get them back to being sharp while still getting rest for their aging roster, which is clearly a tougher task. They’ve had a series of bad starts and a couple of shaky third periods. Linus Ullmark is looking a little more human as well.

It’s not the time of year to be overtinkering but at the same time, Montgomery can’t ignore the trouble either. He’s pressed the right buttons all year. His first year in a new coaching job was the best in Boston since Alex Cora in 2018. But the Bruins’ dominance to this point has raised the bar to where anything short of a Stanley Cup is a disappointment this year, especially given the age of the roster.

Mazzulla’s task is tougher.

He famously became the coach unexpectedly after Ime Udoka was suspended and eventually fired for his actions off the court right before the start of the season. Udoka led the Celtics to the NBA Finals and Boston entered the 2022-23 season as the favorite. The Celtics should get credit for putting character over coaching skill, but Udoka’s ability to spur the players and get them to defend isn’t easy to replace.

Under Mazzulla, the Celtics still played up to those lofty expectations for most of the season. It earned Mazzulla permanent status after the Celtics took his interim tag off. But since the end of February, they’ve looked awfully ordinary. They’re not defending at the elite level they did last year. They’ve withered in key spots late in games and Mazzulla has made some rotation and clock management choices that have earned him some scrutiny.

Both the Bruins and Celtics have a lot of games in a short time to end the regular season. Montgomery and Mazzulla will both inevitably be judged on how their teams fare in the playoffs. But their success or failure then could be determined by how well they pull out of their current skid to set their team for the postseason.

If the Bruins and Celtics can weather this and get back on track, experiencing this could be a sneaky blessing as they gain evidence of their ability to overcome adversity.

But time is tight and brilliance is fragile.