Kofi Kingston has seen off numerous different challengers in his first reign as WWE Champion, but he could be about to meet his most fearsome yet.First it was Daniel Bryan, whom Kingston fended off at WrestleMania 35 to become the first African-born WWE ever.Then Kofi had to deal with the menacing threat of Kevin Owens, who had turned on The New Day in April, but Kingston dispatched of the Canadian as well.And more recently Dolph Ziggler has been consigned to history after being defeated by Kingston at both Super ShowDown and Stomping Grounds.With Kofi seeing off challengers left, right and centre, you'd be forgiven for thinking that SmackDown had ran out of credible competition for their top prize.

And in a way you'd be right - as the next challenger is from Raw as part of the Wild Card Rule.

That's right - Samoa Joe will be the next man to face Kingston at Extreme Rules, and he made his statement last week on Raw by jumping the champion on the stage and locking the Coquina Clutch in.

He followed that up on Raw on Monday night by putting Kofi to sleep in the middle of the ring as part of a six-man tag match, showing his vulnerability for the first time since his huge achievement at 'Mania.

Of course whenever someone is in a feud with Joe, personal issues and family matters normally come to the forefront, and this seems likely to be no different.

Joe promised though that he would do or say nothing about Kofi's wife and children if he simply shook his hand in the middle of the ring - but Kingston's reaction was not very PG at all.

Kofi went all Stone Cole Steve Austin on the Samoan Submission Machine by 'flipping the bird' at his rival, showing the first signs of an Eric Bischoff-led SmackDown Live.

With Corey Graves' swearing live on-air on Raw and now this, it's clear that WWE are pushing some kind of boundaries, even though both were cut from the YouTube recaps.

WWE may still be PG officially, but don't be surprised if we see more crossing of lines and swears in the coming weeks.