The only good indicators of who will do well on grass are the weather and court conditions. Since the Sampras era, the groundskeepers have made the court player slower, which is why the great modern baseline players have been able to dominate. If it stays really wet and the courts are slick, one of the big servers has an outside chance to unthrone Djokovic.
Now, sorry, for the bad news. Even though I love Federer, all I can talk about is the Djoker.
He is simply playing better than everyone else. He has the best serve return off both sides in modern history (only Agassi and Connors could match him). He moves better than any other player in the game. And he added the one wrinkle where Federer used to have the edge — transitioning from defense to offense. In the old days, Djoko would make a great defensive get, but stay deep in the court. Now watch how often he recovers and moves back toward the baseline. If his opponent doesn’t hit another almost winner, Djoko will step in and go on offense. That’s why he made the jump in 2011. The other thing he does better than anyone is his ability to change the direction of the ball (take a cross court shot and hit up the line). In an age where everyone runs around their backhand to dominate with the inside out forehand, the best backhand up the line will win the match.
He and Murray are basically the same player, except that Djoko’s forehand and second serve are better. I find their matches incredibly boring for this reason. Murray (unless Lendle can get him back to where he was when he first won Wimbledon) tries to outstead Djoko. So they play these hellacious rallies that last forever, but eventually Djoko grinds him down in these five set matches.
Djokovic has a chance to go on an historic win streak. Federer’s too old. Murray’s doesn’t make Djoko doubt himself. Nadal’s out. And none of the younger players have made the jump to challenge him: Raonic, Nishikori, Thiem and Zverev (who beat Fed on grass a week or so ago).
With his incredible conditioning and dietary regime (the same one that turn Navratilova’s transformation from chubby also-ran to ripped champion), he may stay at his current level for another three years. Since the jump at the end of 2010, when he won Davis Cup and beat Federer after being down match point, Djoko has been in the finals of a Grand Slam 17 out of 22 times. You better learn to like him, because he’s all you’re going to be seeing for the foreseeable future.