Rossi is on-loan at Celta from Fiorentina.
"We have not diagnosed it yet but what scares us most is his sensations he's getting," club doctor Juan Jose Garcia Cota said after the game.
"It could be a serious injury.
"We have been exploring the issue and he does not appear to have a big problem, but there is a lot of worry.
"Specifically because of the sensations and the mechanism of the injury, it makes us think that there may be something."