The 29-year-old powerhouse's eighth successive defeat of Cilic set up a clash with 10-times champion Rafael Nadal in the semis.
Argentina's Juan Martin Del Potro felled Marin Cilic in a French Open clash of the titans, winning 7-6(5) 5-7 6-3 7-5 on Thursday, and will now aim his heavy artillery at 10-times champion Rafael Nadal in the semi-finals.
Del Potro has looked one of the biggest threats to Nadal's domination this year, with his pulverising forehand dismantling everyone in his path on the Parisian clay.
After dropping the opening set of his first round match he won the next 12. But Cilic, who like Del Potro stands 1.98m tall, owns a U.S. Open title, has a beast of a serve and always looked like being his first serious test. And so it proved.
After returning to a sunny Court Suzanne Lenglen locked at 5-5 in the first set tiebreak after battle was halted because of rain on Wednesday, Del Potro flirted with danger before racking up an eighth win in succession against Cilic. He appeared almost overcome with emotion after reaching his first French Open semi-final since 2009, when he was beaten by eventual champion Roger Federer.
"Well, it's tough to speak," the 29-year-old, who has risen back to sixth in the rankings after battling back from three left wrist surgeries, said on court as fans sang "Delpo, Delpo".
Asked about facing Nadal, who he has beaten five out of 14 times but never on clay, he was drowned out by his fans.
'BIG LOVE'
"It's a challenge that every player wants to have," he said. "I don't know if I will win, but I will take big love from you and that's most important for me."
The first set always looked key and Del Potro clinched the opener as Cilic blinked first, netting a routine forehand on the second point of the second installment of the match. The second set, like the first, was dominated by serve until Cilic fired himself up to break at 4-4 -- a furious Del Potro throwing his racket at the changeover.
Croatian Cilic played an awful game when serving for the set, making four unforced errors, but he was gifted another chance to serve for the set after breaking Del Potro again and levelled the match at the second time of asking. Del Potro dipped at the start of the third and Cilic had points for a double break. However, the burly Argentine recovered his drive to hit back from 0-2 and take the third set.
Former Roland Garros junior champion Cilic, bidding to reach the semi-finals for the first time after falling in the quarter-finals 12 months ago, kept his nose in front in the fourth. He buckled at 5-5, though, and sent a backhand long on break point, leaving Del Potro to serve for the match, which he did with ease as Cilic missed with three more backhands.
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 "Juan Martin del Potro in action on Thursday")
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