Garbiñe Muguruza led a host of top names into the round of 16 at the Chicago Fall Tennis Classic on Tuesday, as the No.2 seed from Spain defeated Ann Li of the United States 6-4, 6-4 on Stadium Court.

"It was very tight, I think the match was pretty equal," Muguruza said in her post-match press conference. "I’m happy that I stayed calm in the 5-4 game serving for each set, and I managed to close them out."

After three years outside of the Top 10, former World No.1 Muguruza returned to that echelon in July, and the current World No.9 continues to make headway up the rankings as she is in contention for a coveted spot at the WTA Finals in Guadalajara.

Muguruza needed an hour and a half on the dot to oust rising 21-year-old Li, who came into the event just five spots off of her career-high ranking of World No.66.

Stat corner: Li had knocked out former Top 20 player Donna Vekic with ease in the opening round, but Muguruza had the American's number on the day, with the Spaniard converting four of her six break points as she collected her 35th match-win of 2021.

Nevertheless, Li kept close in both sets, and in fact, the American had 15 winners to Muguruza's 13. But Li also had five more unforced errors than Muguruza, and she only converted two of her six break points.

Key moments: Muguruza saw an early 2-0 lead slide back to 2-2, but the second seed reclaimed her advantage in the very next game, breaking for a 3-2 lead after a netted miscue by Li. At 5-3, Li did well to save a set point before holding, but Muguruza came through in the next game, completing a love hold with a forehand winner.

In the second set, Muguruza saw another early break slip away, but at 4-4, she broke Li at 15 after a forehand by the American flew wide. Muguruza closed out the match in the next game following consecutive backhand errors by Li from 30-30.

Next up: Muguruza could face a fellow two-time Grand Slam champion and former World No.1 in her next match: Victoria Azarenka of Belarus. No.14 seed Azarenka will first have to get past American wildcard Hailey Baptiste on Wednesday to set up that clash.

Jabeur, Mertens breeze ahead: Two other Top 8 seeds also made swift passage into the third round on Tuesday.

In the first meeting between two crafty players, No.6 seed Ons Jabeur of Tunisia zipped past Hsieh Su-wei of Chinese Taipei, 6-1, 6-0, to book her spot in the round of 16.

Hsieh had gritted past former World No.1 Kim Clijsters in the Belgian's comeback match on Monday, but she had no answers for Jabeur, who comes into this week at a career-high ranking of World No.16.

Jabeur needed just 46 minutes to oust Hsieh, saving the lone break point she faced on the day. The Tunisian also earned five breaks of service, spurred along by a 76 percent success rate when returning the Hsieh second serve.

No.7 seed Elise Mertens of Belgium also made quick work of her opponent, easing past Ukraine's Dayana Yastremska, 6-1, 6-3, in an hour and five minutes.

World No.18 Mertens was nearly impenetrable on serve during her first meeting with former Top 25 player Yastremska. Mertens won 87 percent of her first-service points and never faced a break point all day. 

Kontaveit keeps winning: After claiming her third career WTA singles title in Ostrava on Sunday, Anett Kontaveit had to travel over a quarter of the way around the globe in advance of her first-round match in Chicago on Tuesday.

But the Estonian zipped past Madison Brengle of the United States anyway in the final opening-round match of the week, 6-4, 6-3.

No.11 seed Kontaveit took an hour and 23 minutes to win her sixth consecutive match and her twelfth consecutive set. All told, Kontaveit has won 13 of her last 14 matches. She has tripled her career title count in the last month, hoisting trophies in Cleveland and Ostrava.

Kontaveit will face WTA debutante Mai Hontama, a qualifier from Japan, in the second round on Wednesday.