Serena Williams roared back from an early deficit to defeat Flavia Pennetta 6-3, 6-2 on Wednesday and book a US Open semifinal clash with Ekaterina Makarova.
Playing in her first Grand Slam quarterfinal of 2014, world number one Williams kept her bid for a third-straight US Open title -- and sixth overall -- alive as she stretched her perfect record over the 11th-seeded Italian to 6-0.
In Makarova she'll face a first-time Grand Slam semifinalist.
The 17th-seeded Russian advanced with a 6-4, 6-2 victory over former world number one Victoria Azarenka -- runner-up to Williams the past two years.
In a battle of two 32-year-olds, Williams denied Pennetta a repeat of her best Grand Slam performance -- a semifinal run in New York last year. But the Italian gave Williams some tense moments in the early going, seizing a 3-0 lead with two breaks of serve in just eight minutes.
World number one Williams responded by winning the next six games to take the first frame in less than half an hour.
Although Makarova is in the final four of a Grand Slam for the first time, she goes in knowing she has beaten Williams on one of the game's biggest stages -- in the fourth round of the 2012 Australian Open.