"He definitely has to consider whether grass has a future for him," three-time Wimbledon winner Becker told BBC Sport.
"I almost thought that he should contemplate not playing this year."
"This is a big, big shock. Nadal has come back from injury so strongly this year but he was playing mainly on clay. Grass is very different compared to the other surfaces. Your movement is different and you have to have healthy legs because you're changing direction, you're slipping and sliding.
"Even though he won all those tournaments, Nadal had been struggling somewhat with the knee and I always thought he might struggle at Wimbledon this year. I almost thought that he should contemplate not playing because he was out for a long time and you shouldn't underestimate it.
"Early on in the match I thought, 'This isn't the Nadal I've seen in Paris, this isn't the Nadal that won Rome'. Credit to Darcis; he took his chance, played aggressively, wasn't afraid, went for the groundstrokes and went for the serve. He kept his composure, wasn't getting too nervous, wasn't getting too crazy out there and and ended up achieving something you don't do every day.
"In a way, maybe it's a good thing for Nadal because if he had been knocked out in, say, the fourth round or quarter-finals it would have put a lot of strain on the legs. Now he has a few more days and weeks off and he can think about his schedule for the rest of the year.
"Nadal wasn't confident in his movement - normally that's his best part. He wasn't confident, he was hitting a lot of unforced errors and I was wondering, 'Why is he making these errors? The ball was there!'. Then I observed a bit better and noticed his foot placement wasn't the way it normally is, especially when he had to move. When he was set, he was good. But when he had to move, he wasn't the same and he didn't have that solid base he had on the clay.
"If you have a knee problem, grass is the worst surface. Hard courts are not as bad because you have a firm position, you can put your foot down and stand up to hit the ball - the bounce is higher so you don't have to bend as low. I wouldn't worry about Nadal playing on hard courts or indoors, but I always thought grass was an issue.
"In terms of his whole career, he has answered the questions. He won the French Open and, in my opinion, is the player of the year so far. He is surrounded by great people and I'm not going to suggest anything to him but, from an outside point of view, he definitely has to reconsider his future on grass."
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A bit harsh but the man has a point.
I watched that match as a rerun and Becker was calling it. On many occasions he basically said that Rafa does not, or was not, playing correctly on grass. My wife and I were like, well Boris this is a former Wimbledon champion, he does not know what he is doing out there.
Becker mentions about not having a solid base to hit from and having to bend down more, which puts Nadal's forehand and health of his knee in jeopardy. Pretty convincing argument.