Torey Krug found himself in rehab mode following off-season ankle surgery. He worked hard during training camp and found his way back into the Bruins’ lineup late in the preseason.

It didn’t take long for Krug’s next setback.

On Monday, during the team’s annual media day, the Bruins announced that Krug suffered another ankle injury. The 27-year-old will miss at least the first three weeks of the 2018-19 regular season.

Bruins GM Don Sweeney confirmed that Krug’s recent ankle woes aren’t related to the fracture that he sustained late last year.

“Torey suffered a left ankle injury unrelated to his previous fracture,” Sweeney said. “He will be in a boot for three weeks and be re-evaluated then.”

The Bruins’ highest-scoring defenseman from a season ago with 59 points (15 goals, 44 assists) left during the first period of the team’s preseason finale against the Philadelphia Flyers Saturday night at TD Garden.

Krug knew something was wrong after his skate caught a divot while taking the brunt of a big hit.

“I had a tough puck in the corner that I was trying to clear out,” said Krug, who tallied a total of four periods this preseason. “My ankle was caught in a grove in the ice, and I got hit at the same time it was a very unlucky thing.”

Reports of Krug wearing a walking boot proceeded following his departure.

Those reports proved accurate as a visibly frustrated Krug spoke to reporters inside the Warrior Ice Arena dressing room.

“Obviously it is unfortunate that I have to go through something like this again but it’s a tough part of our job and something that I’ll have to re-evaluate in a few weeks here,” Krug said about his slew of injuries.

“You work really hard especially throughout the summer to feel comfortable and put yourself in a position to get back in the lineup. It felt like I was just starting to work through timing issues and getting my gap back and then to all of the sudden to have another setback it’s frustrating. It’s unfortunate and very unlucky but its part of it and you just have to work through it and try to have the right attitude.”

Urho Vaakanainen – a standout in training camp – and Matt Grzelcyk hope to fill Krug’s roles on the point and on the Bruins’ primary power play unit during his absence.

Vaakanainen, a 2017 first-round selection, was a pleasant surprise this preseason and will likely appear in Boston’s opening night lineup. Grzelcyk, who spent the last week of the preseason with a lower-body injury, returned to practice on Monday; albeit in a red non-contact jersey.