Despite passing a fitness test on Thursday, he admitted to not being 100 per cent fit heading into the all-important clash against the Welsh - and that became more evident as the game wore on as the former NRL and AFL star's movement became more laboured.
"David's got a bit of a bang on his calf. It doesn't seem too bad," Cheika said.
"He seems OK in the dressing room. Israel, his ankle got a bit weary after last week - (it's the) same injury."
Veteran centre Matt Giteau, who had been dealing with a rib complaint, also finished the match on the bench.
Read more: Courageous Wallabies confident of chances
Cheika admitted he would've taken the brilliant fullback off had he not already cleared his bench.
"We did want to bring him off, in a perfect world we would've brought him off with maybe ten or 20 minutes to go because he hadn't trained all week," Cheika said.
"But we couldn't because of a few things that happened around us.
"He got through the game but the first signs are pretty much the same as last week."
Folau had a mixed evening against the Welsh, appearing to be playing without much confidence in his ankle and having an uncharacteristically poor game under the high ball.
But he came out firing in the second half, making two clean breaks and finishing as the Wallabies' top metre-earner with 64.
-AAP
