Alexandr Dolgopolov knocked two-time champion Viktor Troicki out in the first round on day one of the Sydney International.

Dolgopolov put a Brisbane International quarter-final defeat to Nick Kyrgios behind him by seeing off Troicki 6-3 6-7 (6-8) 7-5 on Sunday.

The Ukrainian will come up against fourth seed Fabio Fognini in round two after serving 13 aces and breaking six times on a searing hot day, winning in two hours and 20 minutes.

Dolgopolov failed to serve out the match in the second set and was unable to convert a match point in the tie-break as Troicki hung in there.

He was not to be denied a place in the last 16, though, breaking for a second time in the final set to send Troicki packing.

Paolo Lorenzi will face top seed Albert Ramos-Vinolas in round two after beating local wildcard Jordan Thompson 7-6 (7-5) 6-4 and Damir Dzumhur defeated Jan-Lennard Struff 6-1 6-4.