Del Potro's flat forehand down the line makes him a dangerous player, believes Roger Federer

Federer beat Philipp Kohlschreiber in straight sets to book a place in yet another Grand Slam quarter final where he will face Argentine del Potro who fought back from two sets down against Dominic Thiem to secure a spot in the round of 8. On the eve of the match, the Swiss maestro talked about his opponent and emphasized that del Potro’s biggest weapon - his thundering forehand - gave him an edge during matches against the top seeds. 

"I think Rafa’s for me is maybe number one," Federer replied when asked if he ranked Del Potro’s forehand as the best in the world as quoted by metro.co.uk.

"It depends on what surface we’re talking about. But just throughout the career, I think Rafa’s is extremely high, if not my favourite one.

"But DelPo’s is flat. When it’s flat, clearly margins are smaller. You also have to be in really good position, court position, to be able to do it, when he can do it from further back, as well. He’s got a great forehand down the line, inside-out forehand, which in my opinion are maybe more difficult shots to hit.” 

Even though Federer enjoys a 16-5 head-to-head advantage against the Argentine, the latter's greatest career moment came against the same player, on the same court, in 2009, when he beat the Swiss to secure his first, and only, Grand Slam. 

"What I like about it, he doesn’t really hold back. He doesn’t care if he misfires a few times. He keeps doing it until he finds his range and his rhythm.

"It seems like a huge takeback, so you always feel like he’s going to be late on it. At the end of the day, he’s in position when he needs to be.

"He drives through the ball perfectly. I think a lot of juniors actually should look at that forehand as a great forehand."