Danielle Collins knocked off former World No. 1 Simona Halep, while Petra Martic and Jil Teichmann notched big upsets and top-seeded Iga Swiatek stretched her winning streak to 24 matches on Wednesday during second-round play at the Internazionali BNL d'Italia at Rome.

The seventh-seeded Collinscontinued her strong season with 38 winners during a 7-6 (1), 6-3 win over Halep.

Collins won 11 of the final 12 points of an 82-minute first set and then won the first four games of the second set en route to the win. The Australian Open finalist saved 9 of 13 break points while advancing to the Round of 16 in Rome for the first time.

"Simona is someone that I've looked up to for a long time, somebody that I really admire as a competitor, and as an athlete," Collins said after the triumph. "I felt like today kind of worked in my favor because I know her game so well from watching a lot.

"I had to come out and play really aggressive and be consistent at the same time, because she's relentless, she gets everything back. I just had to be really patient. There were times I was a little up and down with my serving, so I kind of made some adjustments, and just tried to be not too hard on myself."

Halep, who won the Rome title in 2020, had just 12 winners and saved only 3 of 9 break points.

Collins will next face fellow American Amanda Anisimova, who knocked off 12th-seeded Belinda Bencic of Switzerland 7-6 (5), 6-1.

Martic, a qualifier from Croatia, is in the Round of 16 for the second straight year after posting a 6-2, 6-3 victory over fifth-seeded Anett Kontaveit of Estonia. Martic won 68.5 percent of her first-serve points compared to Kontaveit's 55.6.

Teichmann advanced with a 6-2, 4-6, 6-4 victory over sixth-seeded Czech Karolina Pliskova. Teichmann had some help from Pliskova, who committed 12 double faults.

Kazakhstan's Yulia Putintseva also scored a solid upset, rallying for a 3-6, 7-6 (4), 6-1 win over eighth-seeded Garbine Muguruza of Spain.

Meanwhile, Swiatek continued her torrid play with a 6-3, 6-0 win over Romania's Elena-Gabriela Ruse in just 68 minutes. Swiatek, the defending champion, had a 15-3 edge in winners.

"I'm pretty proud I could get into the rhythm today, just take some lessons during the match and improve my game, game by game," Swiatek said after the victory. "That was pretty solid match for me."

Swiatek will next face 16th-seeded Victoria Azarenka of Belarus. Azarenka defeated Colombia's Camila Osorio 6-2, 6-4.

Second-seeded Paula Badosa of Spain moved on with a 6-2, 6-1 win over Aliaksandra Sasnovich of Belarus. Third-seeded Aryna Sabalenka of Belarus registered a 6-2, 6-0 win over Shuai Zhang of China, while fourth-seeded Maria Sakkari of Greece beat Russia's Ekaterina Alexandrova 6-3, 6-2.

Among other matches featuring seeded players, No. 9 Ons Jabeur of Tunisia beat Australia's Alja Tomljanovic 7-5, 6-2 while 13th-seeded American Jessica Pegula won in a walkover against Ukraine's Anhelina Kalinina.

No. 15 seeded Coco Gauff rolled to a 6-2, 6-4 in over fellow American Madison Brengle.