The goalkeeper has kept back-to-back clean sheets in victories over Bournemouth and West Ham in the Carabao Cup.
Sanchez told the club's website: "I’m feeling pretty good.
"On the team, I think we’re playing the way we want to play. Maresca is passing the message to us quite quickly and I think it’s showing on the pitch, how good we are playing and improving defensively and attacking.
"On myself, I’m feeling the best that I’ve ever felt and after two clean sheets we just need to keep this going. It feels amazing because it’s the fittest I’ve felt in the last two years. Two years ago I didn’t have a pre-season, and last year I didn’t have a pre-season.
"I signed for Chelsea, trained for three days and then played against Liverpool. I wasn’t at my best and played week in, week out, feeling I was at 60 per cent or 70 per cent of what I know I’m capable of. Then the injury happened.
‘But this pre-season I came back two or three weeks before everybody else just to get my knee strong. Now the knee feels like I’ve never had an injury there and I’m just focused on training because I want to give my best.
"I know what I’m capable of, I know how much better I can get, especially with this team and these players, this coach with the way he supports me on the pitch. We can win things and I want to win things with this club. I’m feeling at my best, better than ever."