It makes you wonder what the original plans would of been if Rollins, Cena, Sting, Orton, DB, Cesaro, etc all weren't injured. I feel like Triple H vs Reigns definitely wouldn't of happened if Rollins and Cena were still in the mix.
Well, before The Rock and Ronda were out of the picture, the rumored Wrestlemania card (as far as the top four or five matches go, anyway) as of around mid-August to about early-September was:
Rock/Ronda vs Triple H/Stephanie (or Rock vs HHH and Ronda vs Stephanie in separate matches)
Brock vs Undertaker III
Shield triple-threat or Reigns vs Cena for the WWE Title
Bray vs Sting
...Which would have been a pretty great card, speaking objectively. Funny how many were hoping at the time that we'd end up getting something different than what I wrote above, yet looking at the way things are shaping up now, most would have probably preferred that we had gotten this compared to whatever we're gonna get.
With Rock out, HHH vs Rollins was definitely the back-up plan, and then, of course, the rumored card continued to go through other permutations thanks to the piling on of several unforeseen circumstances: Rollins' injury, them deciding to blow off Brock and Taker's rubber match at Hell In A Cell for whatever reason, Cena's injury, Sting's injury at Night Of Champions, Orton's injury (it was never rumored, but I think he definitely would have squared off with Bray Wyatt in Sting's absence), etc.