Luxembourg lefty Gilles Muller is the first man through to the semi-finals of the Sydney International, having outsted second seed Pablo Cuevas in straight sets.

Muller reached the final four of the Sydney tournament for a third straight year by beating world No.22 Cuevas 7-6 (7-5) 6-4 in one hour and 36 minutes.

Muller will battle two-time defending champion Viktor Troicki for a place in the final.

Troicki was set to face Philipp Kohlschreiber on Thursday but the German withdrew from their quarter-final, citing a back injury.

Cuevas saved six set points during the first set, including two in the tiebreak, but the Uruguayan couldn’t prevent Muller taking the early advantage.

Both players held serve throughout the opening set but the match opened up soon after. Muller broke for a 2-1 lead in the second set, only for Cuevas to immediately break back.

Muller broke again for a 4-3 lead and never looked back.

The 33-year-old, who opened his Australian campaign with a loss to Jared Donaldson at the Brisbane International, has never progressed beyond the fourth round of the Australian Open.