By Matthew Geagan, CBS Boston

BOSTON (CBS) — Throughout their countless frustrating struggles during the regular season, the Celtics were hoping that they’d have a healthy squad when the postseason arrived. Seeding never seemed to matter to the team, although it absolutely should have mattered, as long as they still had that hope of being at full strength during the playoffs.

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But banking on health is like banking on a sunny day six months down the road. And unfortunately for the Celtics, it doesn’t look like many sunny days are in their future. Their postseason dreams have never been darker than in the present, and they turned into a nightmare on Monday night.

That’s when the Celtics announced that Jaylen Brown is out for however long the season will last, shut down with a torn ligament in his left wrist. It subtracts one of Boston’s best players from the equation, one of the few the Celtics could count on each and every night to deliver. Brown had a career year in just about every offensive category, and he continued to ascend as one of Boston’s best defensive players.

Now he’s out of the mix, crushing any hopes of a healthy team or a lengthy stay in the postseason. Brown had to take on a bigger role throughout the season to make up for Gordon Hayward’s departure, which he handled glowingly. Now it’s up to Evan Fournier to take Brown’s place in the starting five, and rookie Aaron Nesmith to continue his recent hot streak off the bench to help mitigate the loss of Boston’s second-best player.

In previous years, losing an All-Star would give the Celtics a little extra juice. It would motivate the team to say nay back to the naysayers and pull a run a run out of thin air. Playing with house money was usually Boston’s best bet. Now they just take that money and run. Injuries are used as an excuse, not motivation. And for a team treading water to simply make the playoffs, they now have a giant excuse to let the season end without much resistance.

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There’s no reason to believe this current crop of Celtics can use Brown’s injury to flip that proverbial switch. If they were capable of pulling that off, they would have done so on Sunday when Brown was out of the lineup for a must-win home game against the Heat. Instead, the Celtics let Miami pummel them to the tune of 72 first-half points, and now they find themselves firmly entrenched in the play-in picture.

If there is a switch with this team, it doesn’t work. It hasn’t been hooked up to anything all season, and at this point, it’s too late to call in an electrician.

Maybe the Celtics can conjure up a little bit of luck and avoid the play-in. That starts Tuesday night when they host the Miami Heat again. A win would provide a slight glimmer of hope, but the team would still need to win at least two of their final three games (Wednesday at Cleveland, Saturday at Minnesota and Sunday at New York) and hope the Heat also lose. That could happen, considering the Heat play Philadelphia and Milwaukee.

But a loss on Tuesday would basically secure a spot in the play-in. The Celtics would need to win their final three games and hope the Knicks lose their final three games to avoid that fate. The Celtics would once again be counting on something out of their control to lend them a hand.

All season long, the Celtics have been counting on things that might happen. It created a cushion that they found far too comfortable, one that the Celtics casually fell back on for large stretches of the season. Each time, it was a little bit harder to get up.

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This time, it feels like the team will remain down and go out without much of a fight.