Roger Federer anticipates a contest akin to a grand slam final if he meets Stan Wawrinka in the quarter-finals of the Rotterdam Open this week – a match that will decide whether he becomes the world's number one ranked player once again.

After success at the Australian Open in January, 36-year-old Federer is now out to take number one spot from Rafael Nadal – with the Spaniard's hip injury providing the Swiss with a window to haul back his old rival.

Federer begins his campaign against world number 121 Ruben Bemelmans before a second round encounter against Karen Khachanov or Philipp Kohlschreiber.

The 20-time grand slam champion only has to reach the semi-finals of this week's competition to take his place at the summit of men's tennis again – and faces the possibility of a match with countryman Wawrinka to decide his fate.

"I would love to be in that position with anyone, but with Stan it would be like a grand slam final, a big-time match," Federer said, AFP report. "I am hoping to get to number one and hoping to do it this week. You always want to do it the tough way. It is not easy to get there.

"The achievement would be quite incredible, it is exciting to see Stan in my section and it is great to have him back."

Wawrinka underwent knee surgery last July, returning to action in late December before reaching the second round of the Australian Open. He reached the semis in the Sofia Open last week, only to suffer elimination to Bosnian qualifier Mirza Basic. He begins his campaign in Rotterdam against unknown Dutch wildcard Tallon Griekspoor.

Federer leads his countryman 20-3 in their head-to-head record, winning their last meeting in the final at Indian Wells last year. Wawrinka's last victory came in the 2015 French Open at the quarter-final stage on route to winning the competition.

If Federer can reclaim top spot, he will extend his record for most weeks at the top of the rankings, which currently stands at 302, while he will also replace Andre Agassi as the world's oldest world No.1, a record the American held when he was 33.