The Czech eighth seed produced a commanding display of controlled aggression and brilliant serving to defeat the world number four 6-3, 6-3 in their Group One encounter.

World number eight Noskova was composed throughout the contest, breaking Gauff's serve four times in the opening set alone as she outmuscled one of the tour's finest movers.

The 21-year-old committed just a single unforced error in a dominant second set and fittingly sealed her victory with an ace to secure her place in the last four on her tournament debut.

Speaking to the crowd in California after the match, Noskova offered a lighthearted reflection on the atmosphere during the contest compared to the celebrations afterwards.

"Thank you guys for the cheers I'm getting now – but it was a little weaker in the match, guys, I'm not going to lie," Noskova joked. "I feel like I stayed in the match through every moment, from beginning to end."

The triumph marks the sixth top-10 victory of the season for Noskova, who claimed her maiden Grand Slam title at Wimbledon in July and won the Berlin Open earlier in the year.

Gauff endured a difficult day on serve, hitting eight aces alongside eight double faults and winning only six of 24 points behind her second delivery.

Despite the defeat, the fourth-ranked American can still qualify for the semi-finals from Group One alongside compatriot Jessica Pegula.

Pegula kept her own qualification hopes alive earlier in the group by claiming her first victory since September with a 6-2, 7-5 win over Ukrainian alternate Marta Kostyuk.

The American made just five unforced errors compared to Kostyuk's 17 in a scrappy encounter that featured seven breaks of serve before Pegula secured the decisive break at 5-5 in the second set.

Kostyuk, who only discovered she would be participating on Saturday after world number one Elena Rybakina withdrew due to a viral illness, has now been eliminated following two defeats.

Kostyuk had also struggled with a wrist injury since August as she attempted to find rhythm and consistency against Pegula in the low-quality encounter.

Noskova now moves forward to face Pegula in her final group match on Thursday, while Gauff prepares to take on Kostyuk as the round-robin stage concludes.