American teenager Coco Gauff showed why she deserves to be at this year's WTA Finals with a commanding 6-0 6-3 victory over Martina Trevisan at the Guadalajara Open.

The fifth seed clinched her maiden spot at the season-ending WTA Finals on Wednesday and backed that up by securing her third WTA 1000 quarter-final on Thursday.

Gauff reeled off the first nine games of the match against Trevisan, where she triumphed in one hour and one minute. The 18-year-old came under pressure from Trevisan, who generated nine break points for the match but Gauff saved all bar one of them.

World number one Iga Swiatek (47) is the only player to have won more matches this year in straight sets than Gauff (32).

Gauff will face Victoria Azarenka in the quarter-finals after the Belarusian toppled 13th seed Madison Keys 6-4 6-7 (4-7) 6-1 in two hours and 13 minutes.

Two-time Australian Open winner Azarenka swept aside Keys in 32 minutes in the third set after a titanic battle in the opening two frames, winning 26 of the 37 final-set points. Azarenka's quarter-final appearance is her 34th since 2009, with only four players having more during the span; Agnieszka Radwanska (42), Simona Halep (39) and Caroline Wozniacki (36).

Third seed Jessica Pegula advanced to the last eight with a 6-4 6-4 victory over former US Open champion Bianca Andreescu.

The American, who survived three match points against Elena Rybakina on Wednesday, trailed early against the Canadian but took control of the match. Pegula will face Sloane Stephens in the quarter-finals after she toppled 2022 US Open semi-finalist Caroline Garcia 7-6 (8-6) 7-5.

On the day her WTA Finals berth was confirmed, seventh seed Daria Kasatkina lost 6-2 2-6 6-3 to Anna Kalinskaya in two hours and 14 minutes.

Fourth seed Maria Sakkari fought back to win 5-7 6-3 6-3 over 14th seed Danielle Collins, while Marie Bouzkova copped a bagel before triumphing 0-6 7-5 6-3 over Liudmila Samsonova.

Sakkari will next meet eighth seed Veronika Kudermetova who beat Jelena Ostapenko 6-4 6-4. Bouzkova will take on Kalinskaya in the last eight.