Portuguese keeper Sa saved Aleksandar Mitrovic’s 81st-minute penalty after Rayan Ait Nouri’s challenge on Bobby Cordova-Reid.
Sa, in his second season at Molineux after joining from Greek side Olympiacos, ensured Lage’s side had something to show for their efforts after dominating for large parts of the match.
Lage said: “Jose had a fantastic season, the pre-season wasn’t good for him because he was recovering (from injury).
“He had just one (pre-season) game against Sporting, then against Leeds and today he came with that save.
“I’m happy for him. He needs to continue to work because he can be one of the good names in the Premier League.”
Lage said Sa had blamed himself for Leeds’ equaliser in last week’s opening-day defeat when Rodrigo’s low shot beat him at his near post.
“This is football,” Lage said. “The last game we were talking about Jose because he wasn’t happy with the first goal (against Leeds).
“Now he did a save and gave us a situation that we did not concede a goal. Football is about that, about the good things players can do.”
Lage was happy with all aspects of his side’s display against Fulham on a baking hot afternoon, apart from their inability to convert chances.
Pedro Neto and Hwang Hee-chan both saw first-half efforts saved and Morgan Gibbs-White missed the best chance of the match when he failed to convert Ait-Nouri’s low second-half cross.
Lage, who said he had been pleased with new £27.5million signing Goncalo Guedes’ cameo role off the bench, added: “I think we deserved to win the game, but we need to score goals.
“We had plenty of chances to do that. Sometimes our players faced a goalkeeper, twice the goalkeeper was not in the goal, I think with Neto and Morgan.
“These are clear chances to score goals, so in the end we look for the performance. Again, another good performance.”
Fulham boss Marco Silva placed no blame on Mitrovic for failing to convert his late penalty.
“Mitro knows that the next penalty he’ll be there, he will take it and he will score,” Silva said. “That is part of the game.
“Last week he had one and he scored. This afternoon it was the moment to win the game, but ok, it’s part of our job, the life of a footballer.”
Silva, whose side have taken two points from their first two top-flight games following promotion, added: “It was a tough game, like we expected.
“It was against a good side playing their first home Premier League match of the season against a newly-promoted side.
“We controlled more or less well during the game, but with the ball we have to be better.”