Acapulco, Guerrero, Mexico, 25 February 2016 | AAP

Bernard Tomic is the sole Australian remaining at the ATP Tour’s Acapulco Open in Mexico after the world No.21 saw off France’s Adrian Mannarino in straight sets to gain a spot in the quarterfinals.

Fifth-seed Tomic beat the world No.58 6-4 6-4 on Thursday to set up a showdown with either American Ryan Harrison or Ukrainian Illya Marchenko.

The 23-year-old Queenslander started the second-round match slowly, losing serve in the opening game of the first set before finding his rhythm to break back twice to claim the advantage.

The second set remained on serve until Tomic broke his opponent in the final game of the match.

His path to a fourth singles title became easier after Alexandr Dolgopolov knocked out top seed and world No.8 Spaniard David Ferrer in straight sets.

Tomic is the only Australian remaining in the tournament after compatriots Sam Groth and John Millman both lost their first-round matches.