Aurélien Collin has been a thorn in the Union’s side for much of his eight years in MLS.

Now he’s a thorn on the Union’s side.

The burly French centerback — 6-foot-2, 169 pounds and plenty of fire — joined the Union on Tuesday after spending the offseason as a free agent.

After early career stops in Scotland, Greece, England, and Portugal, Collin moved to America in 2011 to join Sporting Kansas City. He won the 2012 U.S. Open Cup and 2013 MLS Cup there. At the end of 2014, Kansas City traded him to Orlando City ahead of the club’s first year as an expansion team. After two years in Florida, Collin was traded to the New York Red Bulls. His contract there expired after last season.

The 32-year-old has a green card, so he won’t take an international spot on the roster.

“I had a couple of offers outside, but I wanted to stay in MLS,” Collin said after his first day practicing with the Union. “It’s been an amazing journey. Of course, like in life, there’s ups and downs, but I love this league. I love the playoffs.”

Collin has a knack for goals, in part because his size makes him a threat on set pieces. He’s scored 17 times in 217 games on this side of the Atlantic.

He also has a well-earned reputation for physicality, with 57 yellow cards and five red cards during his years here.

“I’ll be the first to say he wasn’t always my favorite [to face] because he was such a competitor, and that’s a compliment,” manager Jim Curtin said. “And he’s been a champion in MLS, and that’s also something that we thought was important to bring into our locker room — that pedigree, as now we strive to win the bigger games.”

Collin, 32, likely won’t be a starter for the Union. Auston Trusty and Mark McKenzie have those jobs locked up. And if the Union play a three-back formation, Jack Elliott would be next in line to take the field. But Collin will provide substantial depth, especially if McKenzie goes to the Under-20 World Cup in May and June.

“We were exactly looking for somebody like him in order to guide our guys,” sporting director Ernst Tanner said. “But he’s also able to play.”

Collin’s lessons to his younger teammates might include a few tips on the subtleties of defending’s dark arts. Union midfielder and captain Alejandro Bedoya wouldn’t mind that.

“Even the first day in training, I was trying to stay away from him before he’d get stuck into me,” Bedoya said with a laugh. “He’s got that bite to him that these guys can learn a little bit from. ... He’ll be a great presence on and off the field.”