Apart from his mastery on the tennis court, former world number one Roger Federer is also known for the humorous side among his peers, which again came to the fore ahead of the quarter-finals of the US Open.Federer won his fourth round clash against Philipp Kohlschreiber at the Arthur Ashe Stadium in straight sets, with the scoreline 6-4, 6-2, 7-5, and guaranteed his place in the last eight.Although, he had to recover from a minor back problem for which he even took a medical timeout after the second set during the contest.Meanwhile, the opponent of the Swiss maestro was confirmed earlier in the evening as Juan Martin del Potro produced an impressive display to outlast Dominic Thiem in a five-set thriller.The Argentine star battled fever and at one point was two sets down to his Austrian rival.He saved two match points and made a sensational comeback to win the tie 1-6, 2-6, 6-1, 7-6(7-1), 6-4 in the three hours and 35 minutes classic.Cheered on by the Argentine contingent among the crowd present on the Grandstand court, Del Potro hit a number of massive forehand winners throughout the match.And one particular shot hasn’t escaped the watchful eye of Federer, with a hilarious twist to it as well.Taking to social media, the 36-year-old posted on Twitter a video of Del Potro hitting a forehand winner past his counterpart, however, just when he was about the strike the ball, the racquet turned into Thor’s hammer.He captioned the clip: “Juan Martin del THORtro @delpotrojuan”The comparison with the Norse God perfectly epitomises the display of the 24th seed, who overcame adversities to set up another epic contest against the world number three.You can watch the video below!

Nonetheless, an enticing challenge awaits in the quarter-finals as we gear up to witness a repeat of the 2009 final in New York.

However, Federer will be hoping the result comes in his favour this time around as he aims for his 20th Grand Slam title.