Intro:

Bernard Tomic lost a decisive 28-point deciding tiebreaker as Gilles Muller battled to a 7-6 (7-3), 7-6 (15-13) win in their Apia International Sydney quarter-finals on Thursday. Before that match, Mikhail Kukushkin beat defending champion Juan Martin Del Potro 7-6 (5), 7-6 (3).

Script:

Defending champion Juan Martin del Potro was beaten in the quarter-finals of the Sydney International on Thursday.

The Argentine lost in straight sets, 7-6 (5), 7-6 (3) to Kazakhstan qualifier Mikhail Kukushkin.

Del Potro, the 2009 U.S. Open champion returning from an 11-month injury layoff, needed a wild-card entry to get into the main draw because his world ranking had dropped to 338.

Kukushkin will play another Argentine, Leonardo Mayer in semi-finals after he beat Julien Benneteau 6-3, 7-6.

Later in the day Luxembourg's Gilles Muller emerged victorious in his match against Bernard Tomic, despite a tenacious effort from the Australian spurred on by a highly partisan crowd.

Muller clinched the first set tiebreak by a comfortable margin of four points, but the decider in the second set was a different matter altogether.

Both players produced a number of impressive winners but, with Tomic one point ahead, Muller produced the vital three winners he needed to see out the match in two sets, 7-6 (3), 7-6 (13).

Muller will now play Serbian qualifier Viktor Troicki for a place in the final.