The Czech, who will face Bernard Tomic in the next round, has also insisted that he had the energy to go the distance against the South African.
"It was a hard, tough one, especially the end of the fourth set. I'm happy with the way I handled it and I conserved some energy to play five sets if I needed," he told BBC Sport.
"I had to be extremely focussed and patient, you can go so many games watching the ball go past you playing Kevin. I just had to wait for my chance."
Berdych finished runner-up at Wimbledon in 2010.