The Czech goalkeeper hailed the perfect display from the must-win game, suggesting that the Gunners will benefit greatly from a win of such magnitude.
"We played really well and we had to make sure we were in the game and we found our chances," he said.
"Then we hit the crossbar and we finally got a goal. In the second half we knew we needed a second for the result and obviously we had a great goalscorer today in form and we know that when we score goals that everything is easier. At the back we were magnificent."
He added: "Well it is a massive win for us, the club, the supporters and for the future because it will give us confidence.
"We wanted to go through and we obviously left it really late but to win this game against a very good team like Olympiacos and away [from home]... we knew winning the game was not enough, we had to score two goals and we did that."