By Brian Robb, CBS Boston

BOSTON (CBS) — For all the depth Danny Ainge loaded the roster with this season, one area the Celtics are still lacking is on the wing.

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Jae Crowder is the team’s only reliable two-way player on that front, after emerging as the top return piece in the Rajon Rondo trade last winter. He has shown already he can handle defending the size and shooting ability of threes such as Carmelo Anthony or LeBron James, while also holding his own as a decent supporting part within the offense.

That’s not to say Brad Stevens doesn’t have other options at the wing; they just aren’t necessarily natural fits. Evan Turner operates more as a guard than a small forward and his size limits his ability to check bigger 3’s defensively. Conversely, Jonas Jerebko has seen some action at the wing this year, but his size makes it challenging to stick with speedier small forwards. He’s best suited to play the stretch four, where he can pull out bigger defenders away from the basket.

Due to these realities, an understandable hush came over the TD Garden crowd as Crowder was helped off the floor by his teammates late in Friday’s win over the Wizards. The veteran forward was struggling to put pressure on his left knee after a collision with a Wizard in the fourth quarter, the same knee he injured in the postseason against the Cavs last season.

The pain was evident in Crowder’s face as he left the court, making some wonder if he had done damage to the ACL or MCL in his knee. Luckily, the news from team doctor Brian McKeon was good for the Celtics after Crowder went to the locker room: a simple bone bruise.

Following the contest, the 26-year-old sounded confident that any absence due to the injury would be brief.

“Someone kneed me in my knee-to-knee. Knee in the inside of the knee. It didn’t feel good. … I’ll be fine,” Crowder said after the game.

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The situation was more of a scare than anything else, but it certainly highlighted an ugly ‘what if?’ scenario if Crowder was sidelined for an extended period. The former Marquette star has already formed one of the best perimeter defenses in the league alongside Avery Bradley and Marcus Smart. Together, the trio has helped anchor a unit that has forced turnovers at a higher rate than any other team in the early going.

“[We are] trying to be active,” Crowder said of the trio’s defense. “Trying to get into the ball and set the tone and take a little bit off our bigs. Guard-wise it’s going to be a challenge each and every night, we just have to step up to it and that’s what we’re trying to do.”

On a team that’s full of uncertainty up-and-down the rest of the roster, the stability Crowder provides at small forward fresh off a five-year, $35 million contract is something the rest of the roster is searching for.

“We’re still trying to figure it out,” Crowder admitted. “I feel like it’s tough. It’s tough. Hopefully our coaching unit gets it going fairly quickly. It’s tough. I’m not going to lie to you. As a player it’s very tough to get a rhythm and know where you’re going to play so hopefully those guys are winding it down.”

Stevens took a strong step in that department with a new-look rotation in the win against the Wizards, but it’s important not to overlook how much of a bullet the team dodged by not losing Crowder for an extended stretch.

For a team with no clear cut MVP, Crowder’s fit on the roster makes him pretty indispensable for the time being.

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Brian Robb covers the Celtics for CBS Boston and contributes to NBA.com, among other media outlets. You can follow him on Twitter @CelticsHub.