Torey Krug rehabbed through training camp and found his way to the Bruins’ lineup in the second to last preseason game against his hometown Red Wings on Wednesday. Just three days later, his status is back in flux.

Krug, who missed the first week or two of camp following off-season ankle surgery, exited stage right with a lower-body injury during the first period of the Bruins’ preseason finale with the Flyers on Saturday at TD Garden. The veteran defenseman did not return following his 5:28 of ice time.

This is far from an ideal scenario for Krug and the Bruins entering their season-opener with the defending Stanley Cup Champion Washington Capitals Wednesday night. At best, the Bruins could be just playing it safe with Krug. At worst, well, let’s just say it could be an extended absence.

The latter may very well be the case after a tweet from The Athletic’s Joe McDonald.

Krug spotted in a walking boot.

— Joe McDonald (@JoeyMacHockey) September 29, 2018

Head coach Bruce Cassidy didn’t provide any comment on the extent of the injury, nor did he say whether or not Krug’s exit was related to his previous ankle injury.

“He left the game [during the] first period. Intermission I was told he wasn’t coming back. Lower body injury. I haven’t seen him since,” Cassidy said following the B’s 4-1 loss to the Flyers. “I was just watching the highlights of the third period, so, lowlights I guess is probably a better term, so I have no idea. I assume if there’s something there it’ll be updated tomorrow.”

Cassidy and the Bruins coaching staff face important decisions as opening night looms. Saturday’s loss did little to provide any clarity for certain position battles, including the second line right wing vacancy left by Rick Nash, the third line center spot, and a potential replacement for Patrice Bergeron should he not suit up in the nation’s capital.

An extended absence for Krug only adds to the coaching staff’s lineup conundrum. Yes, 2017 first round selection Urho Vaakaninen impressed the Bruins’ brass throughout training camp and Matt Grzelcyk is coming off a solid rookie season. But there’s no denying the Bruins would miss Krug’s puck-moving prowess and offensive creativity on the back end, especially on the power play.

Grzelcyk is similar to Krug in terms of stature and on-ice style. Vaakaninen is a bigger body who is projected to be a solid two-way defenseman at the NHL level. Both have high ceilings, but neither are as proven as Krug.

“I’m not really sure what was going on there, but he is a huge part of our team. On the ice, off the ice, locker room guy, he’s one of the best there is,” Charlie McAvoy said about Krug. “He really unites the team, and obviously, as far as hockey goes, he’s one of our best defensemen. So, hopefully, he’s fine and it was just precautionary because he is someone we need every night.”