Casillas, restricted mainly to Champions League outings by new coach Carlo Ancelotti this season, responded to speculation that he might leave the club with a string of world-class saves in an epic battle against the Italian champions.
His performance, arguably the best on the Real side, earned congratulations from opposite number Gianluigi Buffon, another talismanic goalkeeper.
"I'm happy Gianluigi Buffon offered me his congratulations at the end of the game," said Casillas, 32. "These days it's difficult to get into the team so when I have the opportunity to play I have to be at my maximum level in order that the coach keeps faith in me.
"It's not easy only playing every two weeks but that's the way it is."
Casillas, who hinted last month he could leave the club if he did not get more opportunities, brilliantly stopped Pepe from scoring an own goal, saving with his feet from six metres' range after the defender diverted Paul Pogba's flicked cross towards goal.
He also used his feet to stop a downward Claudio Marchisio header after the Juve midfielder outjumped Marcelo to get to a Carlos Tevez cross at the far post.
Another pick from an outstanding crop was in the second half when he managed to stop another Marchisio effort at point-blank range.
"Casillas did really well tonight," said Buffon. "His saves helped his team to get a draw. It won't be easy for us now but we'll do what we can to qualify."
- Sports & Recreation
- Gianluigi Buffon
- Carlo Ancelotti