John Cena has been having back issues, described as bulging discs in his back holding him back from going at full strength.
Originally, WWE planned on making a WWE Raw title match between John Cena and Sheamus, but changed the match to Sheamus vs. Randy Orton. The reason for this could be that Cena didn’t feel physically 100% for a PPV main event match, and can more easily hide his injury as part of the Royal Rumble Match.
credit: Wrestling Observer.com