(Gary Wiepert/Associated Press)

Defenseman Jack Hillen’s NHL career had been marked by an unfortunate string of injuries, some even falling under the category of “freak accident,” and over the offseason came the latest setback. He exited another shortened hockey season because of lingering knee pain, and when the issue remained after several weeks of rest, doctors started performing tests and scans to figure out the cause.

Those found nothing, until they tried removing the plates and screws left from an old broken knee, wondering if those were the root cause. Underneath the plates, in the screw holes, doctors found the makings of a staph infection.

“I was on antibiotics for a month,” Hillen said Monday. “Ever since I got that taken care of, I feel so much better … I’m 100 percent, ready to go. I feel strong, back to where I was before the injury. It gives me closure, because now I know why I was having pain when I came back and played, why I wasn’t feeling well. Now I feel like I’ve jumped back. I can turn. I can skate. I feel so much better. I’m really excited for this year.”

Now, unless someone curious happens across the knee scar and asks Hillen, he doesn’t talk about the injury and barely thinks about it either. A week after undergoing a procedure, he could walk without pain, something once impossible after games. He began riding the exercise bicycle for some cardio, even though doctors told him to lay off. And when the screw holes and plates “filled in,” his flexibility returned to normal. Today, he could run, jump and skate without issues.

“I don’t know if that’s normal,” Hillen said. “It’s a blessing that they found it and I have closure on why I was having so much pain when I was playing last year. I’d get done with a game and I couldn’t even walk, it hurt so bad. I feel great. Really excited.”

The injuries reached critical mass last season, when first Hillen suffered a fractured tibial plateau that kept him out for 60 games and later suffered a concussion after colliding with Alex Ovechkin. Add in the broken jaw caused by an Ovechkin slap shot and the broken ribs caused by a Vincent Lecavalier hit, and the 28-year-old has already endured a lifetime of pain.

On Monday, though, Hillen was upbeat, ready to compete for a roster spot with training camp around the bend. He is entering the second and final season of a two-year deal worth $700,000, and reunites with his old coach in Nashville, Barry Trotz.

“He’s a total pro, in and out of the lineup sometimes and he doesn’t miss a beat,” Trotz said. “He’s such a good skater. His game is about skating and transporting the puck. He’s a really good pro. You look at the group, he’s a useful player and he’s a good player.”

Hillen had equally glowing remarks about Trotz.

“When I was in Nashville, we were the most detailed team I’ve ever been on in terms of everyone knew their responsibilities,” Hillen said. “He wrote it out on the board. If you didn’t know what you were doing out there, it was 100 percent the player’s fault because he was very detailed and had everything written out. The most detailed coaching staff I’ve played on was in Nashville. I think that’s good. Everyone will be on the same page.”

Trotz has lumped Hillen into the mix for the sixth starting blue-line spot, along with John Erskine, Dmitry Orlov, Connor Carrick, Nate Schmidt and Cam Schilling. The first five spots are set, Trotz said, but everything beyond that is up for grabs.

“Best depth we’ve had since I’ve been here,” said Hillen, who has played just 36 games with the Capitals since signing in 2012-13. “I’m battling hard to get on the ice. That’s good. But I’m not going to sit back and be like, ‘Oh, okay take my ice time.’ I’m going to go push and try to get in the lineup. That’s my job. I’m going to battle every practice in this training camp to be that five, six d-man.

“I know I can, because I’m healthy.”