I would predict that Djokovic's rating has further to fall still, but herein we perhaps return to the strength of these types of rating systems: whilst Djokovic may struggle after a lay-off like any other player, he is probably better equipped than most to recover his best form more quickly, something he is trying to do by changing his coaching set-up and re-employing his old mentor, Marian Vajda.
Nonetheless, even with Federer's absence for the third clay court season in a row, I would not entertain backing Djokovic for the French Open at his current odds of around 17.00, viewing him as more of a 50.00-shot.
Thiem the value against solid favourite
This perhaps makes Rafa Nadal's odds of 1.48 look even more appealing. Despite his own struggles of recent years, the Spaniard is the deserved favourite to win his 12th title at Roland Garros. He returned from injury to win two Davis Cup matches at the start of April, before going on to win clay titles in Monte Carlo and Barcelona. At the time of writing he is about to play in the quarter-finals in Rome and looks to be progressing there with his usual imperiousness.
That's not to say that Nadal is a certainty. Dominic Thiem, who beat Nadal in Madrid, has reached the semi-final in Paris for the last two years and, were the two to meet, if narrowing my ratings to only consider clay-court form, Nadal would only be a 1.55 favourite. Now, considering Thiem is available in the outright market at 14.00, he is likely the value bet.
Others to consider are Alexander Zverev (14.00) - profiled recently by Ralph Ellis - Kei Nishikori (65.00) and David Goffin (50.00) who, alongside Nadal, Thiem and Djokovic, complete a clay-court world top-six of players likely to play at the French Open. We'll know more when we see the draw.
What's perhaps most interesting going into the second grand slam tournament of the year, though, is the relatively depressed nature of the men's game. Only four players in my top 20 are currently rated at 95% or more of their peak rating, with only the youngsters, Hyeon Chung and Borna Coric, seeming to be on-the-up. The top four are especially depressed, with the lowest average rating between them that I have ever recorded.