Garbine sets up Serena showdown

Serena Williams will play Garbine Muguruza in the French Open final on Saturday in a replay of last year's Wimbledon title match.

Williams won that in straight sets for her 21st Grand Slam title, but Muguruza, at 22, 12 years younger than the American, has improved further since then.

The top seed and defending champion kept alive her hopes of a record-equalling 22nd Grand Slam title against unseeded Dutchwoman Kiki Bertens.

But her form was at best patchy as she laboured to a 7-6 (9/7), 6-4 semi-final win.

The fourth seeded Muguruza, meanwhile, underlined her fine form with a 6-2, 6-4 win over Australia's Samantha Stosur to reach a Grand Slam final for just the second time.

Bertens went 2-0 up before Williams opened her account. The Dutchwoman failed to convert a set point at 5-3 with Williams serving and then a pair of drop shots in the next game brought up a break-back point for the American which she converted with a big forehand drive.

Bertens appeared to be having trouble with an injury to her left calf muscle as Williams took the lead for the first time in the match, but she held firm to force a tie-break, which Williams went on to win 9/7.

The pair exchanged service breaks to get the second set underway and Bertens then failed to take two break points to get to 4-2. Minutes later Williams grabbed the break she needed to put the match away, needing four match points in the end.

The final will be the fourth match in four days for Williams due to the bad weather that has dogged Roland Garros this week.

Muguruza, who is the first Spanish woman in 16 years to reach the French Open final, was in command against 32-year-old Stosur, a former US Open champion, from the start but had difficulty putting away the match from 5-2 up in the second.

"Emotions can sometimes be bad when you make a final," said Muguruza who defeated Williams in straight sets in the 2014 French Open second round.

"Sometimes you just have to stay calm, prepare youself as best you can and play with no regrets."

With the Suzanne Lenglen court barely half-full, Muguruza shrugged off the ghostly atmosphere as well as the bone-jarring 13 degrees to sweep the first set in 32 minutes.

There were was no let-up in the second set as Muguruza, a quarter-finalist in the last two years, carved out a fifth break of the match for 5-2 after a sixth double-fault by Stosur on her way to sealing victory.