Pistolesi captured her last 12 matches for the longest active winning streak on the WTA Tour. But she could not come all the way back against Capriati, who moved on with a 6-2, 5-7, 6-1 triumph.
A former Australian and French Open champion, Capriati has played 14 tournaments this season but is seeking her first title. She was runner-up at Miami and Stanford and is seeded sixth at the U.S. Open, which begins Monday.
Former U.S. Open champion Lindsay Davenport, the top seed, returned to the semifinals with a 6-0, 7-5 victory over Spain's Magui Serna.
Davenport has not dropped a set as she tries to reach the final for the fourth straight year.