The chaps are warming up.

Delpo joins one Rafa Nadal in the semi-final – they will play on Friday. Here is how the Spaniard came from a set down to beat Diego Schwartzman earlier on Thursday.

Delpo served the third set out to love and Cilic, playing as the aggressor, goes long on the first three points of the game to put Delpo in touch of the semi-final. Three successive unforced errors give the Argentine three match points. He needs only one, with a thunderous serve allowing him control of the rally to claim his spot in the semi-final.

Delpo bides his time, pushing Cilic around the court, to craft three break points. The Croatian fends off the first but, after a backcourt battle, Delpo takes the second of the three on offer and will serve for a spot in the semi-final.

Delpo races into a 40-0 lead but Cilic, as he has done for much of the match, goes after Delpo’s second serve to cut the arrears to 40-15. However, the Argentine produces another glorious drop shot to seal the game.

A very, very solid hold from Cilic. This set had a tie-break written all over it. *Cue break of Delpo’s serve.*

There he is. Delpo holds to love, sealing the game with a pretty special drop shot. Glorious, effortless stuff from the Argentine.

Cilic, despite trailing in the match, is looking the more comfortable on the clay. The 29-year-old holds to 30, and the pressure is back on the Delpo.

Some pretty superlative baselining from both players in the sixth game of the fourth set. But it is Delpo who emerges with the hold. The Argentine found the line with a trademark forehand on his way to holding there, only his third winner of the match.

Cilic races into a 30-0 lead behind some solid forehand hitting but then hammers an overhead smash into the net to bring it back to 30-30. A fine serve out wide to Delpo’s backhand allows the Croatian to re-take the initiative at 40-30 and a long Delpo forehand gives Cilic the game.

Del Potro gives Cilic a sniff of a potential break with a double fault at 40-15 but then thunders down an ace to level it up at two each.

Easy holds for both players to open the fourth set, though Delpo looking the more composed as his hold is to love.

Well who saw that coming 15 minutes ago? Del Potro serves out to love, making it five games in a row and two sets to one. Cilic hasn't fallen apart, but does, it seems, need to be playing close to his maximum to live with a player who, in the end, is quite a lot more skilled than he.

Cilic has gone! Not for good, but suddenly he's looking unsettled and playing loosely. As Rafael Nadal seals his win over Diego Schwartzman on Lenglen, Del Potro is back in control of this match despite barely controlling his own game, never mind his opponent's.

Delpzington is motoring suddenly, serving hard and oiling that forehand for 40-15. A devastating second serve doth follow, right into the body, and Cilic can't get close to controlling his return, sending a backhand towards the chair. The question now is whether Del Potro can parlay the momentum he barely earned into something set-decisive. What a phrase that is, my apologies.

Cilic errs on the forehand, but quickly makes 15-all; he is playing far more aggressively than Del Potro, whose tactic of staying in points isn't working anymore. Still, Cilic is no metronome, and with Del Potro at 15-30, he has him off balance and makes another forehand error; two break-back points ... and Cilic goes wide with the backhand! They're back on serve and Del Potro hasn't even had to play well to get there! What an oversight that is from the Croatian!

At 15-0 Del Potro opens his shoulders to hit one of those forehands, only for Cilic to retort with a beast. Del Potro then misses an easy overhead, dumped into the bottom of the net, and is probably relieved when he finds himself at deuce. He's not feeling good out there, but krichs to a hold.

Another service game in the books for Cilic, whose hooked forehand down the line is working really well. Del Potro did coax himself to 30 though, so he's not getting cleansed out there, and will know that all it takes is a bit of pressure and a couple of good shots to get us back on serve.

Del Potro hasn't gone, but he's thinking about ordering an Uber. He finds himself yet another break point down, saves it, and quickly closes out the game; that's a huge hold, because Cilic isn't good enough to dominate him over the rest of this, then another set. If he hangs in there, he can win from here.

Here comes Del Potro. They reach 30-all and he hits aggressively, pressurising Cilic into clouting a forehand against the net cord. But he can't force the break and Cilic performs a holler and skip, quickly wrapping up the game with an ace.

Cilic is in the ascendancy now, quicker around the court and looking like he's enjoying being out there. Quickly it's 0-40, Del Potro in danger of losing three service games in a row row row, but he muscles two points, the second won with punishing backhand. But when he needs a first serve, he can't find one - he's missed them all in this game - and ends up netting a backhand. Momentum is all with Cilic now - will Del Potro feel sorry for himself, or will he change things and start to attack?