Piers Newbery
BBC Sport at Roland Garros

""Oh, Andy!" It's a familiar anguished cry for anyone who was on Chatrier last night but this time it's Andrea Petkovic, not Andy Murray, who's indulging in a bit of self-admonishment. The German missed much of 2012 and 2013 with a succession of injuries and says she still has a long way to go to get back to her top-10 form. Taking out the fourth seed and reaching the final is a big ask."

Image source, AP

Andrea Petkovic is hanging in there. Just about.

She is pegged back from 40-0 as Halep exploits space on her forehand side and then a forehand of her own lies wide for 40-30.

She keeps the nerves locked down and the lid on Halep, luring her long, to seal the game. She is ahead on the second set scoreboard, but not in too many other departments.

Simona Halep is metronomic. Each stroke is almost identical in technique, each shot landing similarly close to the baseline.

It is a tune that is doing Andrea Petkovic's head in. The German takes her frustration out on her bat as she nets in the final rally.

This is more like it from Andrea Petkovic.

She gets her longer limbs levering some serious power into the ball and manages to pierce Simona Halep's defences twice with clean winners to move 40-15 up.

She closes out, but can she keep hitting so big, so accurate, so often?

Matei Alexianu:, external Romania's biggest talent since Ilie Nastase. Fantastic to watch.

Joel:, external This could easily be a R2 match rather than a semi-final, the way Halep is dominating a nonexistent Petkovic.

Piers Newbery
BBC Sport at Roland Garros

"She might not be a big world name, yet, but Halep has enjoyed one of the most astonishing rises through the ranks in women's tennis over the last 12 months. The Romanian was ranked 57th in the world when she lost in the first round at Roland Garros last year. Since the she has won seven WTA titles and will move to three in the world if she wins today."

Image source, Reuters

Simona Halep lands a sumptuous forehand pass en route to 15-40 and two set points with just 25 minutes of the match gone.

Andrea Petkovic briefly holds back the tide seeing off both of those and another from deuce, but a framed return gives Halep a fourth chance.

Petkovic is desperately lashing at the ball to try and keep Halep backed up behind the baseline, but in her eagerness she sends a forehand long.

K, at work hardly working, via text: Marsha's mental strength makes her the worst opponent ever you could face in a three setter- kudos to Genie though, she will go far.

Anonymous via text: Chin up Bouchard that was a great match, you had a great tournament and a great future ahead grand slams for sure.

Simona Halep is only five foot six inches, but he stretches that frame to cover all corners. Andrea Petkovic is having to go for the finest winners to kill her off in rallies.

On this occasion the German manages to string together enough winners to take the game, but Halep's form means she is going to have to maintain a stratospheric standard to stay in the match.

Andrea Petkovic shows signs of making a fight of it at 15-30, but Simona Halep is finding angles that just don't compute for the German.

A beautifully timed forehand streaks across a despairing Petkovic as she hold again to move to within a game of the set.

Philippe Chatrier is turning into an abattoir and Andrea Petkovic is the one being put through the mincer.

The German cannot lay a finger on Simona Halep and loses her serve to love, This is brutal, beautiful stuff from Halep.

Fourteen minutes on the clock and Halep has won 17 points to Petkiovic's seven.

Simona Halep is flowing and right now Andrea Petkovic is bobbing downstream and out of the tournament.

The fourth seed sweeps away a superb forehand, striking straight through the centre of the ball and ratcheting down an ace in a hold to love.

Image source, Reuters

Andrea Petkovic is on the board but under pressure. Even when she wins a game it is Simona Halep making the running.

The Romanian is well on top.

Court Philippe Chatrier is half empty as its patrons head off in search of refreshment after the Sharapova-Bouchard ding-donger.

They better get back here sharpish because Simona Halep is not hanging around. She races to 40-0 amid a flurry of squeaky clean forehands before clinching the game.

Tally ho! Andrea Petkovic's serve is immediately being hunted as Simona Halep steps in, hits out and takes a 0-40 lead for three break points.

Petkovic belatedly cranks into gear winning her first point behind second serve, but Halep does let her off the ropes pummelling away a decisive forehand.

Right, Andrea Petkovic to serve. Let's get it on...

Christian Smith:, external As Genie Bouchard's conditioning improves, she will become a significant force at every grand slam. Phenomenal talent.

Ray Allger:, external Whatever you think of Sharapova, her screaming, her life off the court etc, you can't fault her fighting spirit or bottle

McEnroe may be giving away that piece of advice for free to Andy Murray, but Murray has not been on the blower to offer him a fully paid-up coaching role. Yet anyway.

You can listen to the American legend's answer to whether he would say yes to such on offer on BBC Radio 5 live's website's In Short section.

In the meantime though John McEnroe has been pondering tomorrow's men's semi-final between Rafael Nadal and Andy Murray and believes the British number one will have to go through the pain barrier to win.

"Every shot matters and it's going to be a battle," the 55-year-old seven-time Grand Slam champion told BBC Sport.

"You've got to accept the fact that you're going to be feeling pain but you have to convince yourself that that feels good. If you get past that, you've got a shot at it."

You can hear more John McEnroe on BBC Radio 5 live sport from 19:00 BST.

Whether it is Simona Halep or Andrea Petkovic in the final opposite Maria Sharapova is the big question.

The answer will be hammered out on the Philippe Chatrier clay next up.