Roger Federer is one win away from becoming the oldest man to secure the world number one spot after the Swiss 20-time Grand Slam champion saw off Philipp Kohlschreiber of Germany at the ongoing Rotterdam Open.

The 36-year old defeated Kohlschreiber 7-6 (10-8) 7-5 on Thursday night to reach the quarter-finals.

Federer will replace Rafael Nadal as world number one if he beats Robin Haase in their last-eight tie on Friday.

On the possibility of securing the world number one spot, Federer said: “I’ve struggled to try and get there. I had to win a lot of matches.”

On his duel with Kohlschreiber, Federer said: “Tonight was complicated, I had to fight and struggle.”

“I had a good gameplan going in, but I was never able to completely pull it off.” he concluded.