Li Na serves in the game.
China's top tennis player Li Na withstood a late comeback from Petra Kvitova to beat the fifth-seeded Czech 6-3 7-5 on Friday and set up a Stuttgart Grand Prix semi-final with American qualifier Bethanie Mattek-Sands.
World number five Li was put under early pressure by a series of brilliant Kvitova groundstrokes but responded by rattling off five consecutive games to claim the first set.
World number eight Kvitova took a 2-0 lead in the second set by breaking Li's first serve game. However, the second seeded Li bounced back again, reeling off another five straight games.
The Australian Open runner-up then twice had her serve broken as the mercurial Kvitova blasted a string of superb service returns past her opponent to level at 5-5.
A fine volley and a brilliant return from an unimaginable angle put Li 6-5 ahead and she finally went through on her third match point when the Czech netted a backhand.
American qualifier Bethanie Mattek-Sands, who advanced with a 6-4 6-2 win over German Sabine Lisicki, will be Li's opponent in the last 4 clash.