I would rather rest Messi than any other player. I believe he's still not recovered from his injury. Leave him on bench and play Rafinha instead. At least we will be able to evaluate how Rafinha looks on his natural position. Also I'd like to see duo Rakitic-Xavi for at least 60 minutes. Xavi might fit current tactics than Iniesta, it's time to find it out.
I don't get why Rakitic plays these type of games and is on the bench in banana peel type ones.
Especially since he somehow has 0 stamina to play a few matches in a row why not play him against Celta, rest him against Almeria then use him in all 3 difficult games next week.