Rotterdam Open

The Swiss maestro, who last held the top ranking in November 2012, will return to the summit if he reaches the semi-finals at the ATP 500 event.

After seeing off Ruben Bemelmans in the first round, two-time champion Federer came through 7-6 (10-8) 7-5 against Philipp Kohlschreiber in a hard-fought battle on Thursday.

That secured his place in the last eight, before Haase overcame fellow Dutchman Tallon Griekspoor 6-4 6-0, fighting back from a break down in the opener and rescuing three break points in the first game of the second before cruising through.

Frenchman Jo-Wilfried Tsonga knocked out top seed Marin Cilic to reach the semi-finals of the Rotterdam Open on Friday afternoon.

The 2011 runner-up will take on Czech Tomas Berdych for a place in Sunday's final after upsetting Cilic 7-6 (10-8) 7-6 (7-5) in just over two hours.

Tsonga converted on his fourth set point in the opening set tie-break with a trademark forehand winner down the line before the big-hitting Frenchman took his opportunity in the second set tie-break to record his first win over Cilic since August 2011.