Roger Federer will meet Jo-Wilfried Tsonga next after beginning his grass-court season with a 7-6 (7-1) 6-3 win over Australia's John Millman in Halle.

Federer, 37, lost to Millman at last year's US Open and was given a thorough work-out by the world number 57.

Neither offered up any break points in the first set and, after Federer had swept the tie-break, the Swiss secured the only break of the second set.

Tsonga beat Federer in an epic five-set comeback at Wimbledon in 2011.

The French world number 77, who overcame compatriot Benoit Paire 6-4 7-5 in his own first-round match, also beat Federer in the pair's two most recent matches.

In total, Federer leads their head-to-head record by 11 wins to six.

"It is always important to win your first game on grass, because otherwise the grass season can be very short," said Federer, a 20-time Grand Slam champion, after his win.

German Alex Zverev, who hurt his knee in his win over Robin Haase on Monday, has withdrawn from the tournament's doubles draw.

The second seed however remains in the singles and will take on American Steve Johnson on Thursday.

Defending champion Borna Coric coasted to a comfortable 7-6 (7-2) 6-3 win over Spain's Jaume Munar and will play Portugal's Joao Sousa next.