NEWPORT, R.I. — Seventh-seeded American Jack Sock and third-seeded Australian Lleyton Hewitt advanced to the semifinals at the Hall of Fame Tennis Championships Friday.

The 21-year-old Sock, fresh off a doubles title at Wimbledon with Canadian Vasek Pospisil, defeated top-seeded and two-time Newport champion John Isner 6-4, 7-6 (4). The 33-year-old Hewitt beat American Steve Johnson 6-4, 6-4.

The two will meet in the semis on Saturday after induction ceremonies honoring the 2014 class into the International Tennis Hall of Fame, which is highlighted by Lindsay Davenport in the recent player category.

The other semifinal is second-seeded Ivo Karlovic of Croatia against Samuel Groth of Australia. Both advanced on Thursday.

Isner won the 2011 and 2012 Hall of Fame titles and had victories in 14 of his previous 15 matches on Newport’s grass courts.

Serena out of Swedish Open

STOCKHOLM — Swedish Open organizers said defending champion Serena Williams will not appear at the tournament next week because she doesn’t feel on top form.

Tournament spokesman Marcus Duner said Friday that the top-seeded American had decided to use one of her two allowed annual withdrawals, with Williams saying in a statement that she was “still not at 100 percent.”

At Wimbledon, Williams couldn’t get the ball over the net in a doubles match with her sister Venus, stopping after three games because of what was called a viral illness.

Williams told organizers she was sad to miss Bastad.

“It was my favorite spot to play last year and I am deeply saddened I cannot return,” she said.

Her withdrawal moves South African Chanelle Scheepers into the main draw.

Halep in Bucharest semis

BUCHAREST, Romania — Top-seeded Simona Halep defeated Spain’s Lara Arruabarrena 6-3, 6-1 on Friday to advance to the semifinals of the BRD Bucharest Open.

Halep will play fellow Romanian Monica Niculescu on Saturday. The unseeded Niculescu upset eighth-seeded Polona Hercog of Slovenia in a 6-2, 2-6, 7-6 (3) victory.

The other semifinal will be between second-seeded Roberta Vinci of Italy and Slovakia’s Kristina Kucova.

Vinci beat Petra Cetkovska of the Czech Republic 7-5, 6-3, while Kucova defeated Montenegro’s Danka Kovinic 6-4, 1-6, 6-3.

Man arrested after threats

PRAGUE — Czech police said they arrested a man who allegedly made threats against Wimbledon champion Petra Kvitova.

Police spokeswoman Gabriela Holcakova said Friday that a 23-year-old Czech made the threats against “a publicly known person” in a phone call to an unspecified other person on Thursday. Holcakova would not confirm Czech media reports that the targeted person was Kvitova.

Kvitova’s spokesman Karel Tejkal said nobody had threatened the tennis player directly, but added: “Police did a great job.”

Holcakova said the man, who was not identified, was arrested as police considered the threats serious.

The incident follows criticism of Kvitova, including from a member of parliament, for moving from the Czech Republic to Monaco to avoid higher taxation.

Kvitova beat Canada’s Eugenie Bouchard on Saturday for her second Wimbledon title.

Fognini, Bautista Agut win

STUTTGART, Germany — Defending champion Fabio Fognini eased into the semifinals of the Mercedes Cup on Friday with a 6-4, 6-3 victory over Colombia’s Santiago Giraldo.

Fognini saved the only break point he faced and converted two of his six chances to beat the seventh-seeded Giraldo in 81 minutes,

The top-seeded Italian, who is bidding to reach his fourth final of the season, next faces the third-seeded Roberto Bautista Agut, who beat Spanish compatriot and No. 6 Guillermo Garcia-Lopez 3-6, 6-4, 7-6 (1).

Berlocq upsets Ferrer

BASTAD, Sweden — Defending champion Carlos Berlocq upset top-seeded David Ferrer in a 6-3, 6-3 victory at the Swedish Open quarterfinals Friday.

The 31-year-old Argentine, who won his first ATP world tour in Bastad last year, defeated Ferrer in 85 minutes.

Third-seeded Fernando Verdasco reached the semifinals with a 7-5, 6-3 victory over fellow Spaniard Pablo Carreno Busta.

Errani, Petkovic reach semis

BAD GASTEIN, Austria — Sara Errani overcame a slow start to defeat Chanelle Scheepers of South Africa 2-6, 6-1, 6-3 in the quarterfinals of the Gastein Ladies on Friday.

The 14th-ranked Italian, who won the doubles at Wimbledon last week, was broken three times in the opening set as she won just six points on her serve.

Errani, who was seeded second, dominated play afterward to set up a semifinal against Shelby Rogers, who beat No. 7 Camila Giorgi of Italy 6-1, 7-5.

Appearing in her first WTA quarterfinal, the 147th-ranked qualifier from the United States dropped serve only once while Giorgi hit 11 double faults.

Earlier, Andrea Petkovic reached her third semifinal of the season by defeating Stefanie Voegele of Switzerland 6-3, 6-2.

The fourth-seeded German, who won her first of three career titles here in 2009, broke Voegele’s serve eight times in a match interrupted for 3 1/2 hours by rain at 1-1 in the second set.

Petkovic will next play Grace Min of the United States, who beat No. 8 Karolina Pliskova of the Czech Republic 6-2, 6-1 in just under an hour.

It’s the first WTA semifinal for the 138th-ranked Min, who won two events on the lower-tier ITF circuit this season.