SHANGHAI (AFP) - Roger Federer said thoughts of his near-elimination early in the Shanghai Masters helped propel him to a crushing victory over Novak Djokovic in the semi-finals on Saturday.

The 33-year-old Swiss remembered that during the 6-4, 6-4 win his mind wandered to the second round when he saved five match points against Leonardo Mayer.

"I was thinking about it midway through the match when I was up a set and a break going, 'Hmm, should I be here or elsewhere? I'm here, let's make the most of it,'" he said.

"I still remember how lucky I got. Clearly I feel very fortunate being in the tournament. But that's sometimes how things go.

"Especially when you're playing well, you're confident, you believe, you're happy. I'm mentally fresh from a vacation. I mean, that's even more reason now to keep on trying to win the tournament."

Federer will now return to world No. 2 and he will be favourite for an 81st career title when he takes on France's Gilles Simon in Sunday's final.

He said there would be no emotional comedown after Saturday's fervent atmosphere at the Qi Zhong Stadium, but was also not expecting an easy ride against the in-form Simon.

"I don't think there will be a letdown, to be quite honest. You can lose, fine. But I'm not going to come into the match and play terrible. It just won't happen, not in the finals, not against Simon," Federer said.

"He's going to make me play enough shots to feel good. He's not going to blow me off the court. He's going to hit a lot of balls, play with tactics like we know he can.

"But I'm not going to play shocking. I know that. That's the confidence I have right now. But he presents an interesting challenge. He's a different type of guy. He absorbs very well. He anticipates very well.

"I think especially when he's confident like this, he also feels everything he's doing is working, then it's hard to play him."