Brock Lesnar's WWE Championship win was met with an old rival...from the octagon.

In the main event of SmackDown's premiere episode on FOX, Lesnar ended Kofi Kingston's reign as WWE Champion with one F5 right as the match started. Though the big news would have been Lesnar's win over Kingston and how brief the match was, it was eclipsed by the surprise debut of former UFC heavyweight champion Cain Velasquez.

After Lesnar won the title, Rey Mysterio appeared alongside Velasquez and Velasquez ran to the ring and ran Lesnar out as the show went off the air.

Lesnar and Velasquez share plenty of history in the UFC as the two faced off in the octagon back at UFC 121 in 2010. In that match, Velasquez defeated Lesnar by first-round TKO to win the UFC Heavyweight Championship.

But Velasquez didn't come to WWE without some pro wrestling experience. Velasquez had a pair of matches for Mexican promotion AAA in the past couple of months in Mexico and New York City. There's no word on if Velasquez's appearance is a one-time deal or if he has signed with WWE. Previously, it had been reported that Velasquez, who last fought in the UFC in February, had been talking with multiple wrestling promotions, including WWE.

"I'm here because Brock knows what he did, it wasn't right. I saw it. I'm here to get some payback," Velasquez said, referring to Lesnar's beat down of Rey Mysterio's son on Raw.

For a full report on SmackDown, check out Fightful's coverage of the show here and check out the post-show podcast at this link.

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