Four-time champion David Ferrer kept alive one ritual and American Jack Sock tried starting another at Auckland's ASB Classic on Thursday.

The top-seeded Ferrer reached the semifinals for the sixth time after beating Lukas Rosol 6-3, 6-4, and advanced to play Sock.

The 26th-ranked Sock upset fourth-seeded Kevin Anderson 1-6, 6-4, 6-4, and began a new post-match ritual by removing one sock and handing it to a fan.

"We were talking about it in the warm-up today," Sock said. "Jo (Wilfried Tsonga) has got his thing and a few players have their thing, and with such a unique last name that I have we figured I might start a new tradition and give a sock away if I win."

Second-seeded Jo-Wilfried Tsonga advanced to the semis on his first visit to Auckland, but only after a difficult struggle with No. 6-seeded Fabio Fognini. Tsonga won 7-5, 7-6 (4) in a match which turned on single points in the late stages of both sets.

The 10th-ranked Tsonga will next play eighth-seeded Roberto Bautista Agut, who beat two-time champion John Isner 7-5, 2-6, 6-3.

Isner, who served 31 aces in his win over American compatriot Sam Querrey on Wednesday, served 17 on Thursday. But Bautista Agut managed to find the means to cope with Isner's powerful serve.

Rain interrupted and then suspended play at the Hobart International and the Sydney International, where Grigor Dimitrov was leading Alexandr Dolgopolov of Ukraine 4-6, 6-3, 4-2 after frequent interruptions.

Top-seeded Simona Halep led Svetlana Kuznetsova 5-4 in their semifinal, while Monica Puig of Puerto Rico led Belinda Bencic of Switzerland 4-0.

At Hobart, Mona Barthel withdrew from her scheduled quarterfinal against Alize Cornet with a back injury, handing Cornet a walkover. Barthel sought treatment early in the first set of her win over Naomi Osaka on Wednesday.

In a completed quarterfinal, third-seeded Dominika Cibulkova beat Kiki Bertens of the Netherlands 7-5, 6-3.

In the Kooyong Classic exhibition in Melbourne, Nicolas Almagro beat Hyeon Chung of South Korea 6-2, 6-2, and 2006 Australian Open runner-up Marcos Baghdatis defeated Paul-Henri Mathieu 7-6 (3), 6-3.