Ronaldo has allegedly become disillusioned at Real Madrid, with comments from the club's president about trying to sign Neymar being poorly received by the forward.
Welsh worldwide Gareth Bale, who has been plagued by injuries, could make his first start Liga start for over three months against Celta after playing 61 minutes against Numancia.
Real stay fourth in the standings on 32 points while Barca have 48 although they have played one game more.
Celta were given a golden opportunity to restore parity when Keylor Navas conceded a penalty after 72 minutes, but the Costa Rica worldwide atoned for his error by saving Aspas' spot-kick.
Real Madrid announced on Friday that the team captain, Sergio Ramos, has suffered an injury during the training session on Friday. He spotted Navas off his line and chipped him from the edge of the area to make it 1-0.
"We made a lot of errors, we gave the ball away a lot, something we don't normally do and we did it at important moments in the game, when we could have caused them more damage", Real coach Zinedine Zidane told reporters.
Celta Vigo have been struggling this season and they are in need of a positive run of games that would help them to move away from the relegation zone.
Brazilian worldwide Paulinho added an extra shine to the win by tapping in as the game drew to a close.
"We played very well in the first 45 minutes but not in the second half and a game lasts 90 minutes".