Martinez made saves from Dusan Vlahovic and Luca Ranieri in the space of two minutes just before Eddie Nketiah opened the scoring against Fiorentina.
"The more games I play, the more confidence I get," he told Arsenal.com.
"I managed to keep a clean sheet and me and Bernd (Leno) played 45 minutes each, both keeping a clean sheet in the win. I'm delighted with that.
"I personally feel great. The team is looking sharp, we're moving the ball really quickly, we're nice and solid at the back, so bring on Real Madrid."