One day after eliminating fourth-seeded Venus Williams, Jankovic ousted world No. 1 Serena Williams 4-6, 6-4, 7-6 (7-5). Friday's match took nearly three hours and Jankovic fended off a match point before putting the win away.
The match was tight with Jankovic winning 116 points to Williams' 113. There were 13 service breaks, including two by Jankovic in the third set when Williams was serving for the match.
Williams, playing in her first tournament since a long layoff because of a knee injury, went up 5-2 in the tiebreaker before Jankovic stormed back with five straight points.
Maria Jose Martinez Sanchez defeated Ana Ivanovic, 6-4, 6-2 in Friday's other semifinal.
Jankovic, the No. 7 seed, is 1-1 lifetime against Martinez Sanchez. Jankovic won in straight sets last year while Martinez Sanchez's victory came in 2001.
Jankovic is going for her 13th career title while Martinez Sanchez has one championship to her credit.
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