Pennetta advanced to a semifinal against Li. No. 2 seed Agnieszka Radwanska and Simona Halep meet in the other semifinal Friday.
On the men's side, Roger Federer beat Kevin Anderson 7-5, 6-1 in the quarterfinals.
Federer will face Alexandr Dolgopolov, who beat Milos Raonic 6-3, 6-4.
Austrians have a big day on the slopes
WORLD CUP SKIING • On a great day for ski-crazy Austria, Anna Fenninger won her first overall Alpine World Cup title and Marcel Hirscher took a huge step toward his third.
Fenninger's breakout success was expected on Thursday in Lenzerheide, Switzerland, though Hirscher surprised himself on super-G day at the World Cup Finals by beating the master of the discipline, Aksel Lund Svindal of Norway.
Austria can complete its first title double since 2002 when the season-ending slalom and giant slalom Hirscher's strongest events are raced this weekend.
That leaves the nation time to savor Fenninger's success after a second-place finish behind super-G winner Lara Gut built an unassailable points lead over her Swiss friend.
In a race of surprises, Alexis Pinturault's winning run of 1:13.71 as the last racer denied his unheralded French teammate Thomas Mermillod Blondin an even more stunning win by 0.56.
Bode Miller of the United States was a further one-hundredth back in third, repeating his Olympic bronze-medal placing in super-G.
The season for Miller and Svindal ends on Saturday with the GS in which Hirscher also looks to fend off a challenge for the discipline title from Park City's Ted Ligety. The slalom is on Sunday.
Ex-Fiesta Bowl boss sentenced to prison
COLLEGE FOOTBALL • A former longtime Fiesta Bowl chief executive was sentenced Thursday in Phoenix to eight months in federal prison after acknowledging he participated in an illegal campaign contribution scheme. John Junker was sentenced after pleading guilty two years ago to a conspiracy charge in the scheme in which bowl employees made illegal campaign contributions to politicians and were reimbursed by the nonprofit bowl. Bowl employees were reimbursed at least $46,000. Junker, 58, is the only person to face time behind bars as a result of the scandal that jeopardized the bowl's NCAA license and its status as one of four bowls in the national college football championship rotation.
From wire reports