When Stan Wawrinka jokingly called Roger Federer an "a**hole" for beating him in the 2017 Indian Wells final

It is no secret that Roger Federer and Stan Wawrinka are just as good friends off the court as they are fierce competitors on it. The two have locked horns 26 times till date, one of which came in the final of the 2017 Indian Wells Masters.

Seeded ninth in the tournament, Federer defeated three seeded players en route to the final, including an impressive straight-sets victory over 21-time Grand Slam champion Rafael Nadal in the fourth round.

Wawrinka, the third seed, also had to vanquish three seeded players to set up the final against his countryman. Most notably, the 36-year-old triumphed over eighth seed Dominic Thiem in the quarterfinals and 21st seed Pablo Carreno Busta in the semifinals.

The all-Swiss final began in predictable fashion as the 20-time Grand Slam champion broke his opponent's serve in the fifth game to take the first set 6-4.

Wawrinka began the second set much better, breaking the former World No. 1's serve to take an early 2-0 lead. However, the 40-year-old found his groove soon afterwards and clawed his way back to level things at 2-2.

From there, both players held until the 12th game. With Wawrinka serving to stay in the match at 6-5, Federer raised his level and managed to break, securing the Indian Wells title with a picturesque smash. The scoreline read 6-4, 7-5.

The triumph marked the Swiss' fifth title in Indian Wells as well as his 25th Masters crown overall. It was also the 90th ATP singles title of his career.

Speaking in his on-court interview during the presentation ceremony, Wawrinka jokingly called Federer an "a**hole" for being all smiles after denying him the win. This only made the 40-year-old laugh even harder, which in turn made Wawrinka and the spectators join in.

Stan Wawrinka also revealed that he had been cheering for the 20-time Grand Slam champion during the final of that year's Australian Open against Rafael Nadal. Having only returned to action at the beginning of the year after recovering from a knee injury, the Swiss went on to win the tournament.

Adding that he was still his "biggest fan," Wawrinka congratulated Federer on that triumph as well as the one in Indian Wells.

"I'd like to congratulate Roger. He's laughing, he's an a**hole but it's okay. I've lost some tough ones against [Federer] but when you played the final of the 2017 Australian Open, I was still your biggest fan," Wawrinka said. "So congrats on your comeback and congrats for today."

Here's a video of the incident uploaded to YouTube by Tennis TV:

Roger Federer has lost to Stan Wawrinka only thrice in his career so far

Roger Federer has won all but three of his 26 meetings against Stan Wawrinka

Across 26 meetings, Roger Federer has lost to Stan Wawrinka only thrice in his career. The first loss came in the third meeting between the pair, a straight-sets defeat for the 40-year-old at the 2009 Monte-Carlo Masters.

The Swiss followed that loss by winning 11 straight matches against his countryman over a five-year period before losing again at the Monte-Carlo Masters in 2014. Wawrinka's third and most recent victory against the former World No. 1 was in the quarterfinals of the 2015 French Open.

Since then, the duo have squared off seven more times on the tennis court, all of them going in favor of the World No. 27.