By Matthew Geagan, CBS Boston

BOSTON (CBS) — Tuesday night is a must-win for the Boston Celtics. Not in the sense that they’ll be eliminated from the playoffs, Brad Stevens will be fired, and Danny Ainge will suddenly decide to trade away Boston’s promising young stars if the Celtics can’t beat a solid Pacers team in Indiana.

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Life will go on for the Celtics if they lose Tuesday night. But boy, do they need a win, just to remind themselves that they still have the ability to beat good teams.

The Celtics have dropped four of their last five, and those four losses have been costly in terms of the team’s psyche and where they stand in the Eastern Conference. Each of the last four losses have been of the gut-wrenching variety, and making matters worse, each of them came on Boston’s home floor. There were the late-game collapses against Brooklyn and Oklahoma City, two wins the Celtics let slip away with some truly horrendous late-game execution. They lost to the Rockets in overtime, going the final 2:49 without scoring any points. And aside from a run to start the second half, the Utah Jazz beat the Celtics up throughout their victory in Boston last Friday night.

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This slump is Boston’s worst of the year, and if it weren’t for a closer-than-it-needed-to-be win in Cleveland last Wednesday, it would be much, much worse. Granted, the skid has come as Gordon Hayward and Jaylen Brown dealt with injuries, and Kemba Walker has looked nothing like his All-Star self as he returned from a five-game absence with left knee soreness. But the Celtics are crumbling in the moments when they thrived earlier this year, with mental lapses on both sides of the floor littering crunch time. It didn’t used to matter who was in or out of the lineup, the team would rack up wins regardless. That no longer feels like the case.

There’s reason to believe the Celtics can bounce back. Brown will eventually return from his hamstring injury. Jayson Tatum will get used to a life of double (and occasionally triple) teams. Kemba’s knee may never be fully healthy, but the point guard will be better. It’s hard to imagine he’d get any worse than his last four games. Brad Stevens should be able to conjure up some more after-timeout magic. Maybe, just maybe, this March malaise will be beneficial, showing the Celtics they aren’t as great as they — and we — thought. Maybe it will force them to get back to grinding it out for 48 minutes, rather than relying on style and finesse.

But the slump needs to end soon, because it has essentially ended any hope of the Celtics jumping up to the No. 2 seed in the Eastern Conference. Last Tuesday, the Celtics could have jumped over the Toronto Raptors with a win over the Nets. Instead, they collapsed in the final minutes, leading to this skid. They now sit three games behind Toronto in the standings, and just 1.5 games ahead of the Miami Heat for the No. 3 seed.

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With 19 games to play, the Celtics need to get their act together. They follow up Tuesday’s important clash with the Pacers with an even bigger game against the Bucks in Milwaukee on Thursday. They have two games remaining against the Pacers and Bucks, and two more against the Heat (one in Boston and one in Miami). The C’s still have a meeting against the Raptors in Toronto on March 20, giving them a chance to claw their way back into the conversation for the two-seed. But if this skid continues, they may soon be saying farewell to the No. 3 seed as well.

The current reward for being the third-best team in the East is a first-round matchup with the Philadelphia 76ers, a matchup nightmare for the Celtics. The 76ers have been their own worst enemy throughout the season, but they went 3-1 against the Celtics. Philadelphia is currently a game behind the Pacers, so Indiana could also be Boston’s first-round matchup. Either way, the Celtics will run into a sizable foe, the kind of team they’ve struggled against this season.

At the moment, the mood around the Celtics is a cautious one. We’ve seen them play above and beyond expectations for most of the year, and those good graces shouldn’t be lost because of a slump. Just about every good team goes through these stretches, and the great ones bounce back even stronger.

It would be nice to see the Celtics begin that process Tuesday night.