Hair-pulling is generally frowned upon in professional sports, but given the length of some players’ locks — and beards — we’re frankly surprised it doesn’t happen more often.

In the NFL, a lot of guys — Clay Matthews, Larry Fitzgerald, and Richard Sherman come to mind — wear their hair like manes. But in the NHL, especially during the playoffs, bountiful beards are the big thing.

And no one’s beard is more impressive than former Bruins center Joe Thornton, who looks like he just walked off the set of “Jeremiah Johnson,’’ Sydney Pollack’s 1972 film starring Robert Redford as a veteran who goes to live in the mountains.

But all that hair can sometimes be a problem — and it was Thursday when Thornton, who plays for the San Jose Sharks now, dropped his gloves and tangled with Toronto Maple Leafs center Nazem Kadri. The fight didn’t last long, but when it was over, a clump of Thornton’s beard was lying on the ice.

Afterward, a sharp-eyed member of the Sharks training staff retrieved the hair and placed it in a bag for, um, safe keeping? (Honestly, we’re not sure what the team intends to do with it.)

Asked about the incident after the game, Kadri said this: “I have no idea how that happened. I thought I was a hockey player, not a barber. I didn’t mean to grab him there, I couldn’t really reach him. He’s a big boy across the shoulder. I felt like I just grabbed him in the middle of his jersey and came down with a handful of hair.’’

For his part, Thornton seemed entirely unbothered that some of his beard had been ripped out, at least judging from one — possibly Photoshopped — picture.