Here comes the pain.

Former UFC heavyweight champion Brock Lesnar returned to his pro wrestling roots last night on RAW and immediately made an impact by delivering an F5 to John Cena.

It was Lesnar's first appearance on WWE television since he left the promotion after WrestleMania 20, an absence of eight years.  Lesnar was dubbed the "Next Big Thing" by WWE's creative machine during his original run in WWE, but his time in UFC made him a bigger star than Vince McMahon ever could. 

The roof absolutely came off the arena when Lesnar's music hit and the live crowd gave Brock an Austin-like reaction for his return to his roots.  The return was well-done, exciting and Brock is more popular than any WWE superstar currently on the roster.

But what does it mean to WWE moving forward?

It's well-known that Brock does not want to work a full-time schedule for WWE but really, can you blame him?  Lesnar has earned the right to make spot appearances, achieving arguably the same mainstream success in mixed martial arts that The Rock achieved in movies. 

Lesnar is obviously being primed as Cena's next big opponent.  The Rock seems to have closed the book on Cena last night, dismissing him as just an obstacle on his road to the WWE title, but Brock presents a very interesting match from a marketing standpoint.

WWE could easily promote Brock vs. Cena as the biggest name in UFC against the biggest name in professional wrestling.  The mainstream sports reporters are going to have to pay attention to Lesnar's actions (at least initially) and that's never a bad thing. 

Assuming that Lesnar is only going to appear once a month on television, he could still be a viable character who could help WWE.  People pop when they see Brock destroy someone, they've done it since he was a rookie.  No one wants to see Brock give a 20-minute promo about something, they want to see him maul someone and WWE can provide that.

Lesnar has the benefit of having real-life sports credibility as well, so even fans who are too young to remember his first WWE run know who he is and how he is a legit athlete.  Current UFC fans might even be tempted to turn on WWE television to see their former champion in a new role.

Even if WWE does not choose to feud Lesnar with Cena and only used John as a catalyst for his return, Brock's return sets up many interesting matches with current WWE guys. 

Lesnar vs. Punk would be a very interesting "big vs. small" match with Punk bumping around and trying to chop Brock down for a submission.  Lesnar vs. Triple H (even though he's semi-retired) could give fans a money match that they haven't seen before.

Of course, the big match on everyone's mind is The Rock vs. Brock Lesnar, something we saw way back at SummerSlam 2002.  However, both guys have become even bigger stars since that event and a matchup between the two heavyweights could draw huge interest.

In any event, it's great to see Brock Lesnar back.  I am very happy that he found success in mixed martial arts but, selfishly, I always wanted to see him return to WWE.  Now that Lesnar is back, the entire landscape of World Wrestling Entertainment has changed overnight.

Here comes the pain, indeed.