Raonic showed no ill effects from his over two-hour opening match, completed after midnight local time, in taking out the German in straight sets.
The 20-year-old served extremely well, never facing a break point and losing just 10 points on his serve the entire match. The victory also represents a bit of revenge for an earlier loss, as he was defeated by Petzschner in the quarter-finals of the Gerry Weber Open in Halle, Germany before Wimbledon this year.
Raonic will play the winner of Grigor Dimitrov and No. 4 seed Juan Ignacio Chela in the next round. It will be his first meeting with either player.
This is Raonic’s fourth quarter-final appearance of the year.