The club captain twisted his ankle as the PFA Young Player of the Year nominee looked to stretch his hamstring muscle while sprinting, with both being stretchered from the field
The club captain, who missed last season's Champions League final through suspension, appeared to severely twist his ankle after a collision with Villa's Nathan Baker midway through the second half.
Hazard, who created both goals in Chelsea's 2-1 win, went down holding his hamstring after darting down the left flank, forcing Chelsea to finish the game with nine men as all three substitutes had been used and Ramires was dismissed in the first half.
"Maybe we paid too much - John Terry twisted his ankle, we're waiting for the scan to see how serious it is," interim manager Rafael Benitez told Sky Sports after the game.
"Hazard also felt something in his hamstring so again we're waiting for the scan. A pity for the final but at least we won and it was a good game."
The severity of both injuries remains to be seen, but with only four days until the Europa League final, Chelsea will be sweating on the fitness of two key players.