BOSTON — Blood stains trailed down the front of his jersey and around his grey beard, a fitting look for a captain the Boston Bruins describe as a “warrior.” Zdeno Chara couldn’t do much talking after a puck struck him in the face in the second period of Monday’s Game 4, but even as he was advised against playing, his presence on the bench for the third period spoke volumes of his importance in this Stanley Cup Final.

Chara is believed to have a broken jaw, a potentially series-altering injury with his status uncertain for Game 5 against the St. Louis Blues tonight at TD Garden. He didn’t practice Wednesday afternoon, and teammates indicated he wasn’t at the arena. Boston coach Bruce Cassidy seemed to have the most communication with Chara, via text message, and it was “not much,” Cassidy said.

“Obviously Zee’s not here, didn’t skate, so it makes it a little more difficult for him,” Cassidy said. “I’ve always said that: The guys that are skating are obviously a little closer.”

Chara emerged from the locker room for the third period on Monday night in a full cage, sitting on the bench as the Blues scored twice to pull away for a 4-2 win, tying the series at two games apiece. During one stoppage, Chara encouraged his teammates with a few stick taps, and during play, he’d open and close the gate for line changes.

The 42-year-old has been the Bruins’ captain for 13 years, a reliable top-four defenseman the entire time even as his hulking 6-foot-9 frame has stood out in an NHL that’s gotten smaller and shiftier. Boston could get blue-liner Matt Grzelcyk, who suffered a concussion in Game 2, back for Game 5 — he practiced in a non-contact jersey on Wednesday — but losing Chara would be a blow, both for his presence on the ice and off it.

“Of course, when you lose your captain, you try to step up and be good for him,” center Patrice Bergeron said. “It’s the same thing right now: We’re all behind each other and all supportive of each other and that’s why we’re here.”

The Bruins won Game 4 of the Eastern Conference finals against the Carolina Hurricanes without Chara, but the team already had a 3-0 cushion in the series, and when the sweep was complete, Chara joined his teammates for the on-ice celebration. Against the Blues, he’d be especially missed on the penalty kill, where John Moore would likely take on more minutes for a unit that had killed 19 straight penalties before St. Louis scored on the power play in Game 3. If Grzelcyk is cleared to play Thursday night, that gives Boston another puck-mover to help break pucks out against a punishing Blues forecheck, but the Bruins then lose some size and physicality without Chara, an area in which they were already at a disadvantage this series.

“This matchup is not good with Zee out, let’s face it,” Cassidy said. “They’re a big, heavy team. You lose that element. But someone else is going to have to step up and I think we do it as a group.”

That Chara might have played his final game of this season is especially unfortunate considering how impressive he’s been this postseason, leading all players with a plus-12 rating and averaging more than 22 minutes per game before getting hurt. Center Matt Cullen was the only NHL player older than him this year, and as the league has changed with the infusion of youth and skill, Chara has admirably adjusted in ways some of his contemporaries failed.