The 28-year-old arrived from Olympiacos in the summer and had the difficult task of replacing Rui Patricio.
But Sa has exceeded all expectations and after making several big saves to help his side get a point at Norwich, Lage believes he can become a ‘top goalkeeper’.
He said: “He stopped two or three situations. When we lost the ball in a bad moment sometimes we ran from our final third to our box and Jose did well. We spoke about him before the game and I’m not surprised with what he’s doing.
“He came with a big responsibility to replace a goalkeeper like Patricio, but I trust him.
“I’ve known him since he didn’t have a beard and was a baby face at 16 or 17, and now he’s a big man and can be a top goalkeeper.
“I also cannot forget the way Tony Roberts works with him.
“I am very happy with him and very happy also with John (Ruddy) because he works very hard.”
Speaking after the game, Lage called on his forwards to be more aggressive and force through opportunities.
And when pressed further on the issue around his side’s lacklustre performance, Lage insists he has given the attackers the freedom to express themselves.
He added: “We have the players – the wingers, strikers and full-backs we have can create chances, they have freedom.
“That’s why I’m happy with the way we build-up from the goalkeeper, the central defenders and linking with the midfielders.
“But we should be more aggressive in the final third. In situations one against one, you need to face it, don’t worry if you lose the ball. They have the freedom to do that.
“I am frustrated because we started well, but we should do better in the final third. We have players to do better.
“But I am happy with that they are doing and I am there to give them confidence.
“I prefer them to lose the ball creating their own chances than manage and manage the ball.
“We are very solid with three centre-backs and two midfielders, so they have freedom to create those situations.”
Meanwhile, defender Romain Saiss says the forwards need to be more ‘selfish’.
“We try to play the way we prepared, trying to find the space between the lines but I think we have to do more in the final 30 metres because we have not created enough chances and shots,” he said. “The last two games away we can improve a lot. We have to find the solution. We have to find the right space in front and maybe try different things. Maybe we need to be more selfish up front. We will keep this point and the clean sheet and try and win the next game on Wednesday.”