12/18/2011 01:17 EST | Updated 02/17/2012 05:12 EST

Lesnar, Overeem look to decide who's UFC No. 1 heavyweight contender

TORONTO - UFC 141 is a coming out party for two big men, but for different reasons.

Former heavyweight champion Brock Lesnar returns from another layoff due to diverticulitis, an intestinal disease that has twice forced him to put mixed martial arts on the backburner.

Opponent Alistair Overeem makes his UFC debut in a career that has seen him excel just about everywhere else.

The winner of the Dec. 30 main event at the MGM Grand Garden Arena moves to the front of the contenders' line to face newly crowned champion Junior Dos Santos.

"It's going to be a huge thing for me. Finally in the UFC, against Brock," Overeem told The Canadian Press. "An excellent opponent for me. The best wrestler (Lesnar) versus the best striker. You've got two of the biggest heavyweights out there.

"I'm looking forward to it and I think a lot of fans (are) too."

Added Lesnar: "I'm anxious. Ready to get in and get after it."

Overeem (35-11-1) is a slight favourite to beat Lesnar (5-2), according to bookmakers.

The return of Lesnar, who has not fought since losing his title to Cain Velasquez at UFC 121 in October 2010, and the arrival of Overeem, a star in Pride, Strikeforce and K-1, is welcome news for the UFC.

Welterweight champion Georges St-Pierre, the organization's biggest pay-per-view draw, is on the shelf after knee reconstruction surgery. Middleweight title-holder Anderson Silva is also injured and, at 37, is running out of time.

Lesnar been a draw from Day 1 in the UFC. And the chiselled Overeem will be a welcome addition to the always popular heavyweight division if he lives up to past billing.

But both fighters arrive with baggage.

For Lesnar, it's his medical chart.

"We've been getting just nailed with these diverticulitis questions," confided a handler.

For Overeem, confusion over mandated drug tests by the Nevada State Athletic Commission have dominated recent headlines.

Like Lesnar, the Dutch fighter was slated to take a pre-fight test. But things got complicated when Overeem left the U.S. during his training camp to visit his ailing mother in the Netherlands.

Overeem eventually got a licence to fight in Nevada but the drama — and his change in body type over the years — has had people talking.

"He's been fielding nothing but steroid questions all day," said one of his handlers.

The 31-year-old Dutchman takes the complications outside the cage in stride.

"For me, it's all about attitude. I see myself as a very fortunate person being able to have made my sport, my hobby, my work. So yeah life is not perfect, there are going to be issues. There's going to be stuff that you need to do. And I like my job, so I just put it under the same banner — this is part of the job. Chin up ... and get moving."

The six-foot-five Overeem used to fight at 205 pounds as a light-heavyweight, walking around at 215-220 pounds. Now he is right at the edge of the 265-pound heavyweight limit.

He attributes the weight increase to strength and conditioning training and diet.

The six-foot-three 265-pound Lesnar, a former NCAA wrestling champion, was due to face Dos Santos in June at UFC 131 in Vancouver after their stint as rival coaches on "The Ultimate Fighter." But his health issues took centre stage again.

The good news is he says he made the most of the time away.

"I spent some good quality time with the family, got rejuvenated. I'm ready to get back to the nitty-gritty," said the 34-year-old Lesnar.

And he says he feels ready, even if fighting over the holidays is something he hopes to avoid in the future.

"I take my hat off to my family and everybody that has to cater around my schedule," said Lesnar. "My family's got my back.

"We manage, we get through it, and have a good Christmas and give a good Christmas ass-whupping down in Las Vegas."

No stranger to New Year's fights, Overeem went 5-0 in late December in Pride and K-1.

Overeem has not fought since a unanimous decision over Fabricio Werdum in Strikeforce in June. He subsequently parted ways with Strikeforce, which is owned by the UFC, over timing of his next fight, citing a rib injury.

Overeem is unbeaten in 11 fights, a stretch dating back to a September 2007 loss in K-1 to Sergei Kharitonov.