Roger Federer has all but sealed his place in the last four of the ATP World Tour Finals with a straight-sets triumph over Kei Nishikori.
The world number two saved two break points early in the opening set before earning a break himself to open up a 3-1 lead.
Nishikori put up some resistance after that, showing the kind of dogged form at the baseline that saw him beat Andy Murray on Sunday, but Federer was able to hold on and close it out 6-3.
Following a medical time out for Nishikori at the start of the second, Federer went on to assert his dominance as two further breaks allowed him to serve out the contest 6-3 6-2 with just over an hour on the clock.
