The former Nigerian international was speaking after Messi led Argentina to beat Egypt 3-2 in a World Cup Round of 16 encounter on Tuesday.
Speaking on Fox Sports, Mikel wondered what Messi eats.
“Argentina is coming through yet another difficult game, where they have been pushed to the limit. How much has Messi played, how much has been taken away from him mentally, psychologically, physically as well,” Obi Mikel said.
“That’s going to be the question as well, how much can he give again to be able to drag this Argentina team yet again to another semi-final.
“That’s going to be the question, but when you have Messi, I don’t know what the guy eats. I don’t know what he eats because every time you think it is finished, he comes up with something spectacular.”