As we know, John Cena's injury to the achielles tendon is the top story everywhere currently.
Whilst we don't know how severe the injury is, we can analyse recent house show reports.
John Cena and Ryback were working "Tables" matches whilst in the UK. After the Nottingham show in the UK, Cena beat Ryback in a Tables match and had his birthday celebration. From then on, Cena's matches were then changed to Team Cena (Cena, Bryan, Kane) vs Team Ryback (Ryback, Ziggler, Big E).
Cena was obviously being protected with the tag mathes, Cena didn't get involved in last night's Moscow house show match until the very end according to reports from ProWrestling.net and PWTorch.
Whilst it will more than likely revealed on Raw the extend of the injury, note Edge was out with an Achielles Tendon injury for 7 months. If Cena was to take that time off, WWE may seriously have to push stars to fill in the huge shoes of John Cena, love or hate him, he sells.