Thiem is the only man to have beaten Nadal on clay over the past two seasons, including a surprise victory in the Madrid Open quarter-finals last month, but there was no repeat shock on Court Philippe Chatrier as the top seed prevailed 6-4 6-3 6-2.
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The No. 7-seeded Thiem was trying to become only the second player from Austria to earn a Grand Slam title; Thomas Muster won the 1995 French Open.
Thiem did at least remind Nadal of his age, saying; "I can still remember being 11 when (Nadal) won here for the first time and I watched on the TV".
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It was early in his career when Nadal began his habit of biting the championship trophies he wins.
The victory also allowed the 32-year-old Nadal to hold onto the No. 1 ranking, ahead of Federer.
Nadal finished another break in the third game to move in front, while injuring his left middle finger midway through the fourth game. Those conditions might have contributed to the cramping that affected Nadal about two hours into the final, at 2-1 in the third set.More news: Government forced to climbdown to avoid Brexit vote defeat
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He now has three grand slam titles since turning 30.
At 19, he won the 2005 French Open on his debut. I didn't do that previous year, losing to Tommy Haas in the first round having had match points. Nadal said last week that he wanted to keep playing for a while, and if his body co-operates, 15 seems like a realistic possibility.
Spanish tennis ace Rafael Nadal powered past Austrian promising star Dominic Thiem in straight sets here on Sunday, claiming his record-extending 11th title along with an eye-catching 86-2 record at Roland Garros. Of course, I have ambition, of course.
"No, you can't be frustrated always if somebody have more money than you, if somebody have a bigger house than you, if somebody have more grand slams than you".
"In the last two years I lost against good players, so it also always depends on your opponent". "It was just awful misses".
Should the 20-time grand slam champion reach the final at the Mercedes Cup, something he has never previously done, he will replace Nadal as world number one.
But, while you expect finance is a factor in a potential decision to pursue an even more lucrative deal away from Nike, it feels like there is more to this than meets the eye.