Top seed and defending champion Roger Federer was given another stern test before defeating Kei Nishikori 6-4, 7-6 (7/4) in the quarter-finals of the Shanghai Masters here yesterday.

The Swiss has struggled to hit top gear this week, needing three sets to beat both Daniil Medvedev and Roberto Bautista Agut, but looked to be cruising when he went a set and a break up against the Japanese eighth seed.