Novak Djokovic marks 37th birthday with win at Geneva Open

Djokovic was a surprise entry into the ATP 250 event following his shock early exit at the Italian Open earlier this month to Chile's Alejandro Tabilo, two days after being accidentally struck on the head by a bottle.

After the world number one underwent tests, he requested a wild card into the tournament in Switzerland and started his campaign with a 6-3 6-3 win.

It was far from straightforward for Djokovic, who needed 90 minutes to get past the German.

Hanfmann had defeated Andy Murray in round one to end the prospect of a battle between old rivals, but was broken in the sixth game of the first set on Wednesday.

Djokovic claimed the opener after a brief delay due to rain before he made a bad start to the second set and found himself 3-0 down.

The 23-time major winner was able to reassert his control and reeled off the next six games in a row to book his place in the quarter-finals.

Meanwhile, second seed Casper Ruud was taken all the way by Austria's Sebastian Ofner (ATP 45), eventually prevailing 4-6 6-2 6-2.