AJ Styles isn't 100 percent as he prepares for his second shot at the WWE World Heavyweight Championship.

The "Phenomenal One" will battle Roman Reigns for the richest prize in the game at Extreme Rules on May 22 live from the Prudential Center in Newark, N.J. The match will be contested under Extreme Rules, but Styles is ailing heading into the main event clash.

Styles has been dealing with some nagging injuries, which kept him out of the ring during "SmackDown" this week, according to PWInsider. WWE officials are obviously being cautious with Styles since his match with Reigns will be very physical and headline the Payback event.

The WWE also pulled the former TNA World Heavyweight Champion from its live events this weekend as a precautionary measure, according to Wrestlingheadlines.com. Styles is no longer booked to wrestle at Friday's show in Greenville, S.C., Saturday's event in Raleigh, N.C. and Sunday's show in Columbia, S.C.

There has been no word on what the lingering injury is, but it would be a bad time for the WWE to lose another star.

John Cena (shoulder), Seth Rollins (knee), Randy Orton (shoulder) and Bray Wyatt (calf) are among the big draws who are injured, while Daniel Bryan (concussion) retired and Brock Lesnar isn't expected back until around SummerSlam.

Cena, Rollins, Orton and Wyatt are all expected to return within the next month, giving the WWE some hope at getting back to full strength after losing several major stars over the last few months, including WrestleMania 32 season.

Styles has proven to be an amazing addition to the WWE roster, putting on one of the better matches of the night at WrestleMania with Chris Jericho and following it up with a tremendous main event with Reigns last month at Payback.

The leader of the Roman Empire won that encounter, which featured outside interference from The Club and The Usos. The factions are likely to get involved at Extreme Rules as well.

Given the popularity of Styles and the stakes of his main event clash with Reigns next Sunday, it's understandable that the WWE is being cautious with him.

For more content, follow us on Twitter @SportsWN or LIKE US on Facebook.