Brock Lesnar burst onto the scene. He was the most feared man in the UFC, he was the future of pay-per-view and everyone in the world was waiting to see what would happen next. Then, he lost, got injured and faded away.

There comes a time every year where we find ourselves wondering, “What the heck happened to so-and-so?”

Were they outmatched in their fights? Did they get banged up? Or like Joe Pesci in Goodfellas, was it just their time to go?

It seems like all fighters fall victim to at least one of three things at the end of their career: time, injuries or a string of bad luck. Regardless of which one of the three it is, it’s inevitable that every year we unofficially have to say goodbye to fighters who run the risk of no longer being relevant in a division. Sure, we’ll catch them on an undercard again and maybe even the first fight of a UFC PPV, but their days of headlining are over.

Here are the top seven fighters that could fade away in 2013.

7. Chris Leben
The Crippler has been anything but that in his last two fights.  With decisive losses to Derek Brunson and Mark Munoz, Leben hasn’t been able to get back to the form that made him a feared fighter in the UFC.  There is no doubt Leben had a minor career comeback winning three straight in 2010, but since his loss to Brian Stann to start 2011 fans haven’t seen the same fighter. The lights are about to go out on Leben.

6. Quentin “Rampage” Jackson

What has been impressive about Rampage since getting into a title fight against Rashad Evans? In fact, how about name the last impressive victory by the former champion? It might just be when he defeated Dan Henderson to unify the Pride and UFC Light Heavyweight championships and that was nearly five and a half years ago. His next fight is against Glover Teixeira who hasn’t lost a fight since 2006.  If Rampage doesn’t get a win he will end up losing a lot more than relevance in the UFC but could also lose any waning hope that Hollywood could be calling him for another tough guy movie roll.

5. Clay Guida
Losses to Benson Henderson and Gray Maynard have many asking what will happen with Guida.  After an impressive four fight win streak it appears that Guida is up against a wall when he takes on Hatsu Hioka in his next match.  Three losses in a row could see Guida on his way out to pasture in the UFC.

4. Forrest Griffin
Griffin is one of the more likeable people in all of the MMA.  His interviews are typically engaging and his books are hilarious. That’s where the rub begins, as Griffin needs to get back into contention in the UFC’s light heavyweight division.  Griffin will be coming off of a knee injury that forced him out of his last scheduled fight with Phil Davis.  Davis is still seen as part of the newer, younger fighters in the light heavyweight division who are making guys like Rampage and Griffin less relevant.  A few wins this year can put Forrest back on the right track, a few losses and Forrest might become the third mic on the UFC broadcasts.

3. Shane Carwin

Remember the guy with perhaps the best one-punch knockouts in the UFC? Remember the guy that looked like he had Brock Lesner dead to rights?

Remember that guy?

Well we haven’t seen him in action for a while and it’s starting to look like father time and the injury bug are in a two on one street fight against Carwin. Easily one of the most likeable stars of the UFC, Carwin has to get healthy and get some wins. After starting his career 12-0, “The Engineer” is now 0-2 and hasn’t been fully healthy in a while.

2. Josh Koscheck

With 21 fights in the UFC the idea of Koscheck being a contender again is becoming more of a novelty than a reality.  There was a time where he was thought of as one of the best Welterweights on the planet but now is just another guy in the division that new guys aim to beat on their way up and the seasoned fighters hope they can stay on top of.

1. Michael Bisping
It’s too early to grade how good of a fighter Bisping will be at middleweight after his loss to Vitor Belfort but “The Count” will need to impress his next time out in order to stay relevant.  In a weight class that is seen as Andersen Silva and then everyone else, Bisping needs to establish himself as a contender or he’ll he relegated to the undercard and Facebook bouts. The fact remains that Bisping has lost two of his last three and no fighter in the UFC wants to lose three of his last four especially with the rise in young talent. He’s in a division where everyone is working for a chance to knock off the best in the world and Bisping couldn’t get past the second best in the division.  He didn’t get it done at light heavy weight and he has to get it done at middleweight.