Serena beats Bacsinszky 4-6 6-3 6-0
Williams looked unwell for long periods
Safarova beats Ivanovic 7-5 7-5 in 1st semi
Safarova into first Grand Slam final
We catch a quick glimpse of Ana Ivanovic as she prepares to walk out on to a sunny Philippe Chatrier. The Serb, with imaginary racquet in hand, slashes a forehand and then a backhand as she limbers up in the locker room. Then the Serb does some quick on-the-spot sprinting - it is all about the footwork you see. The players are almost ready....
Adam Nicholls:, external Serena in straight sets. Ana is 3-5 against Safarova so it will be tough for her to do it. But I am in #TeamAna all the way!
Image source, Getty ImagesFirst round: beat Anastasia Pavlyuchenkova 7-6 (8-6) 7-6 (11-9)
Second round: beat Kurumi Nara 6-2 6-0
Third round: beat Sabine Lisicki (20th seed) 6-3 7-6 (7-2)
Fourth round: beat Maria Sharapova (second seed) 7-6 (7-3) 6-4
Quarter-finals: beat Garbine Muguruza (21st seed) 7-6 (7-3) 6-3
Total time on court: 8 hours 31 minutes
Average rank of opponent: 27
Image source, Getty ImagesFirst round: beat Yaroslava Shvedova 4-6 6-2 6-0
Second round: beat Misaki Doi 3-6 6-3 6-4
Third round: Donna Vekic 6-0 6-3
Fourth round: Ekaterina Makarova (9th seed) 75 36 61
Quarter-finals: Elina Svitolina (19th seed) 63 62
Total time on court: 7 hours 28 minutes
Average rank of opponent: 73
Piers Newbery
BBC Sport at Roland Garros
"The temperature has leapt significantly to the mid-20s today and Roland Garros is bathed in sunshine, apparently for the foreseeable. You know the weather is good here when there are spectators on court before the match actually starts.
"While Goran Ivanisevic and Carlos Moya take on a couple of ball kids in legends' hi-jinx on Court Suzanne Lenglen, the serious business is about to get under way on Chatrier. There are even people in the VIP box already. And not just staff."
A Scott on text: You're way off with your Ana Ivanovic tip, reckon she will lose worse than Bacinsinszky. A Safarova/Williams final.
Image source, APWhat do you mean you don't know much about Lucie Safarova? Luckily we are here to help.
The Czech leftie is contesting her second Slam semi-final, having lost in the last four to eventual champion Petra Kvitova at Wimbledon last year.
The 28-year-old 13th seed has not yet dropped a set at Roland Garros last year and, of course, beat reigning champion Maria Sharapova in the fourth round.
"She's a great player. She showed that many times. She had a great match against Maria," says Ivanovic.
"It's going to be tough match-up for me. She's obviously lefty, gets really lots of balls back very heavy, very aggressive."
Image source, EPAAna Ivanovic won her first Slam as a 20-year-old at Roland Garros in 2008 - but hasn't really fulfilled her potential since. So understandably she is "very, very thrilled" to reach her first French Open semi-final since 2008.
"It's been a long road and hard work," says the 27-year-old, who was also a Australian Open finalist in 2008.
"Obviously you know seven years ago it was completely different experience. I was a lot younger and I sort of didn't have the experience. I just was so excited and I felt like, you know, I can achieve anything.
"At that point I had so many victories and so many good results. Maybe I didn't appreciate it as much as I do now."
A gentle hum of excitement can be heard across Roland Garros as the French tennis fans head towards the Philippe Chatrier turnstiles. Hope they have plenty of suncream and protective hats in their bags, the sun is shining and the weather is sweet as Bob Marley would say. About 15 minutes until Ivanovic and Safarova are kicked out of the locker room....
Shake up your magic eight ball. Flip your lucky coin. Give you tea bag a predictive poke.
We are after your predictions today.
Come Saturday afternoon, which two of these four players are going to be dirt-wrestling on the terre battue for the title?
Williams v Ivanovic is your banker I guess, but are there any takers for a Safarova v Bacsinszky showpiece?
Hit us on #bbctennis, external on Twitter and 81111 on text with your best guesses and reasons why.
Image source, @RolandGarros/TwitterBonjour mes amis! And welcome to the business end of the French Open - today we are entering semi-final territory.
Four women must squeeze into two final spots.
Either seventh seed Ivanovic or Safarova - the woman who sent reigning champion Maria Sharapova packing - will nab the first one when they meet on Court Philippe Chatrier about 14:00 BST.
And once that match is decided, we will find out if Timea Bacsinszky can cause a shock on the scale of Robin Soderling by beating Serena Williams.
Image source, Getty ImagesHonk, honk! Move out of the way ladies - the Serena juggernaut is powering through Paris.
Maria Sharapova has fallen by the wayside. Petra Kvitova has dived out of the way. Simona Halep has been kicked out of the cab.
Williams might not be cruising along in fifth gear at Roland Garros, but the road ahead is wide open and heading straight towards a 20th Grand Slam singles' title.
Can anyone derail the American? Swiss 23rd seed Timea Bacsinszky will be the latest to have a go later today. And if she can't stop Serena then only former French Open champion Ana Ivanovic or Lucie Safarova - who has not beaten the world number one in eight attempts - are the final roadblock.
Image source, Getty ImagesClose your eyes, relax and let your mind wander forward to this Saturday.
You may picture Lionel Messi scoring as Barcelona ease past Juventus to win the Champions League final.
You may also visualise Serena Williams collapsing to the Roland Garros clay in celebration. And then being presented with the Coupe Suzanne Lenglen after winning the French Open women's singles title.
Williams, like Barcelona, is the overwhelming favourite to stick her mitts on more silverware this weekend. But, as we know, sport has a habit of throwing up the unexpected....