The Ultimate Fighting Championship returns to Madison Square Garden for the second time in the promotion's history Saturday night for UFC 217 (available on Pay-Per-View). The card is headlined by the middleweight title bout fight between champion Micahel Bisping and returning welterweight legend Georges St-Pierre. It's virtually a pick'em according to the folks in Vegas, so it figures to be a hell of a fight.

Here are four things you need to know to get you ready.

It's GSP's first fight in four years

On Saturday, St-Pierre make his return to the octagon after 1,449 days. GSP was one of the top fighters in the world for a decade stretch in the aughts, but abruptly vacated his welterweight title and walked away from MMA in 2013 at 32 years old. It was a strange move, considering the Canadian had defended his title nine times in a row and hadn't lost in his last 12 fights, a streak that lasted longer than six years. But he always described his departure as a hiatus and a "mental break," not a retirement.

"The last two or three fights, I didn't have fun," St-Pierre told Joe Buck in 2016. "I did it because I had to, not because I wanted to and I had too much pressure, too much criticism, too much things for too long and it's very hard when you're world champion, all your life is directed [on that]."

Bisping is a controversial champion

Bisping would have been described as a journeyman fighter until a year or so ago. He was a solid, dependable, middleweight guy who never managed to score a shot at the title. That changed in June 2016 when he pulled off an upset KO of Luke Rocknold to win the middleweight championship. Since then, he's done everything in his power to to hold onto.

To the ire of fight fans everywhere, Bisping has been picky about his fights since winning the title. He took on 46-year-old Dan Henderson last October -- Henderson retired after the fight -- and hasn't stepped in the octagon since. Many fans see Bisping as being opportunistic once again with his second title defense, taking on a man who hasn't fought in nearly four years. Bisping doesn't give a damn.

"I grew up in England, in a humble background. I left school at 16; there weren't many options on the table. It took me a long time to figure out what I would do for money" Bisping said when asked about criticisms of him, according to ESPN. "I said, 'I'll try this fighting thing out.' Here I am fighting in Madison Square Garden, about to get a big chunk of cash."

GSP is making his middleweight debut

Ring rust isn't the only factor working against GSP in his return bout. He'll also moving up weight classes and will be stepping into the octagon as a middleweight for the first time in his career against Bisping, a big middleweight who has fought as a light heavyweight. That's an unenviable task for anyone, even an MMA legend such as St-Pierre. Not only does Bisping hold the size advantage, he's also much more accustomed to fighting at 185 than GSP. But GSP, who has been working on adding weight since April, isn't worried about how he'll feel as a middleweight.

"When guys try to do this, to go up a weight class, they do it in too short notice," St-Pierre told ESPN. "They feel like they carry an extra bag on their shoulder. It makes them more tired. I've been doing this for a few months. The extra weight, the extra muscle mass is already had, so I'm used to it. I'm walking with it right now and it's part of myself."

If he can manage to beat Bisping and win the title, he'll be the fourth multi-division champ in UFC history, joining Conor McGregor. Randy Couture, and BJ Penn.

Endurance is the key

Vegas has the fight as a -160 favorite to go to the cards. Four out of Bisping's last five fights have ended in a decision, as have the last seven GSP fights. All that adds up to a bout that will in all likelihood go the five-round distance.

GSP has almost no shot of knocking out Bisping. He has eight KOs in his career, and Bisping's size advantage makes it highly unlikely St-Pierre can put him to sleep. Instead, expect the tried and true GSP strategy of getting his opponent on the ground, establishing control and wearing him down. That will be difficult with a guy such as Bisping, who has fantastic takedown defense and a seemingly endless gas tank. Add to that four years of rust and 15 pounds he's never fought with before, and you figure GSP will need to have more endurance than ever to go the distance and snag a win by decision.

Bisping on the other hand, actually has a shot at a knockout. He has 16 KOs in his career. Bisping even admitted he'll be going for a knockout and trying to end GSP's return early.

"I'm ready. I've been knocking out sparring partners in the gym," Bisping told Fox Sports. "Here's the thing: Georges St-Pierre, he couldn't knock the bloody ketchup out of a glass bottle. So I'm not worried about that. All he's going to try to take me down and cuddle me to death. And we all know I love a good cuddle."

It's on.

Cy Brown writes about football, golf, soccer and other stuff for Sports on Earth. Follow him on Twitter @CEPBrown.