Roger Federer suffered his first defeat of 2017 on Wednesday in the second round of the Dubai Duty Free Tennis Championships. Federer is blaming his unfamiliarity with No. 116 Evgeny Donskoy of Russia for his shocking upset loss.

The 35-year-old tennis legend entered Dubai as one of the favorites following his Australian Open triumph at the end of January for his 18th Grand Slam Title. He is also a seven-time Dubai champion but it was not enough to knock off Donskoy, who has not defeated any Top 10 players during his career entering the match.

Roger Federer lost 3-6, 7-6 (9-7), 7-6 (7-5) to Donskoy but he had three match points in the second set, per BBC Sport. It was a stunning upset because of the form the Swiss superstar was in entering the tournament.

Federer told reporters after the match that he got tensed and he was not able to play freely as much as he was during the Australian open. He blamed his unfamiliarity with his opponent for his loss. Nevertheless, he praised Donskoy for doing very well against him.

"I just didn't know Donskoy. So many times I just didn't know what his patterns were. I didn't know what his preferences are," Federer said, via ATP World Tour.

"I had my chances. I should somehow close it out. Don't know how it got away, but he did very well. It's a rough one, for sure," he added.

Roger Federer did not use his leg injury as an excuse for his loss to Donskoy. He insisted that he has fully recovered before the match and his fans should not be worried about another injury-riddled season. He missed most of last season due to a knee injury.

The 18-time Grand Slam Champion is set to return on March 9 at the BNP Paribas Open in Indian Wells, California. Federer has a week left to prepare for the tournament and improve his health to remove the doubts in the people's minds.