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In 2014, Roger Federer and Leonardo Mayer produced an epic encounter at the Rolex Shanghai Masters.

A Look Back: Five Years After Shanghai Classic, Federer Faces Mayer Again

Roger Federer and Leonardo Mayer meet for the first time on clay at Roland Garros

It was a crisp October evening at the 2014 Rolex Shanghai Masters, and Roger Federer was embarking on his quest for a first tournament title. The Swiss was coming off a shock semi-final defeat to Marin Cilic just one month earlier at the US Open, and was hoping to get back on track in the Chinese metropolis.

But one unexpected hurdle tripped up Federer as he entered the season's eighth ATP Masters 1000 event: a 27-year-old named Leonardo Mayer. The Swiss had not lost an opening match on hard courts in five years - a streak of 48 straight tournaments. On the other side of the net, Mayer had never registered a Top 20 win on the surface at the tour-level.

On this day, however, the Argentine would play an inspired brand of tennis and push the former World No. 1 to the brink of defeat at the Qizhong Forest Sports City. It was an instant classic in Shanghai and remains one of the most riveting clashes in tournament history. With a flair for the dramatic - and a little luck - Federer saved five match points for a 7-5, 3-6, 7-6(7) victory.

On Sunday, the pair will meet once again, with a berth in the Roland Garros quarter-finals on the line. Federer, who continues his quest for a second title in Paris, will face Mayer for the fourth time in their FedEx ATP Head2Head series. He has captured all three previous meetings and has not dropped a set since that magical evening in Shanghai.

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Flash back to 2014. After splitting sets, Federer and Mayer remained on serve until 5-4 in the decider. Sensing his opportunity to finish off the match right there, the Argentine pounced on Federer's delivery. He would produce two match points at 15/40, moving to the precipice of his greatest victory and one of the upsets of the year on the ATP Tour. But Federer, and the net cord, had other ideas.

The Argentine rifled a backhand at the net-charging Swiss, who lunged for a volley. The response was there for the taking for Mayer. Federer was powerless at the net, with Mayer sizing up a backhand pass down-the-line to finish off the shocking victory. But the shot would clip the top of the tape, hang in mid-air for what seemed like an eternity, before falling back to his side of the net. Even Federer couldn't understand what had just happened.

“I think I got unbelievably lucky today," said Federer. "Let’s be quite honest. I think he deserved it. The first match point was crazy."

A loud murmur rang out from the stands as the Chinese faithful were left in disbelief. Federer was mere millimeters from the exit, but the Swiss was given a magical lifeline. And he would not relinquish the opportunity.

Federer, who made an uncharacteristic 57 unforced errors during the two-hour and 42-minute encounter, saved his best for the critical moments.

"Midway through the third set I was like, yeah, I have been on vacation actually, so it's normal that I'm struggling," Federer said. "I was trying to go for an all-time record of missed volleys tonight."

Federer would take the next three points to hold for 5-all, saving the second match point faced and eventually forcing a deciding tie-break. Momentum seemed to have completely shifted to his side, but Mayer had one last word.

The Argentine surged to a 5/2 lead in the tie-break and earned two more match points at 6/4. Federer turned aside the first with an overhead smash and denied the second - on Mayer's serve - with a backhand pass down the line. It was a mirror image of Mayer's missed opportunity a few games earlier, but this time Federer would not be denied.

After saving one more match point at 7/6, the Basel native celebrated a thrilling victory as a backhand lob caught the baseline.

“Could be my greatest escape thus far. I’ve had some good ones over the years, but this one might just top it all because I was literally out of the point at one stage. I had to come up with some shots that were hard to do anyways. But on match point even more so.”

Four days later, Federer lifted his arms in triumph once again, celebrating his first Shanghai title. He did not drop another set during the tournament, culminating in a 7-6(6), 7-6(2) win over Gilles Simon in the final.

On Sunday, Mayer will have his shot at revenge. And this time, it will be his first chance to topple the Swiss on his preferred surface. Mayer, who has reached five ATP Tour finals - all on clay - is a two-time champion in Hamburg. Six weeks ago, he pushed Rafael Nadal to three sets at the Barcelona Open Banc Sabadell and is coming off his first Top 20 win of the year, defeating countryman Diego Schwartzman in the second round at Roland Garros. The Argentine is ready for another shot at the Swiss maestro.

"The match in Shanghai was one of the most unfortunate moments of my career," Mayer said on Friday. "But this is going to be a good match. I have to play my game and hopefully I enter the court relaxed and ready to go. I am looking forward to this match against Federer. I have a day to get ready, but facing Federer is very difficult, especially with his current form, his talent, his level, everything. It doesn't surprise me that he is in the second week at Roland Garros."