Dimitrov acknowledged Vallverdu for helping him develop a new-found mental toughness, and the duo will hope to build on that victory at the O2 when gracing the hard courts of Melbourne - a tournament where he reached the semis past year.
Federer hailed Nadal for putting up a great fight in last year's Open.
The trio, along with Canadian prodigy Denis Shapovalov, flamboyant Korean Hyeon Chung, Russian dynamos Andrey Rublev, Daniil Medvedev and Karen Khachanov, Croatia's next-gen star Borna Coric and seemingly Australian teenage summer sensation Alex de Minaur head the list of potential grand slam champions in the future.
Can Maria triumph in Serena's absence?
To predict a victor of either of the singles titles is hard.
The first grand slam always brings with it a sense of uncertainty.
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The top 32 players in the draw are seeded, meaning they can't meet until the third round, while the top 16 can't meet each other until the fourth round and so on, with the first and second seeds unable to meet until the final. This leaves several top players who all could potentially lift the trophy at the end of the fortnight, with it being possible to make cases for any of Muguruza, Halep or Pliskova. The seeding for the January Slam was announced on Wednesday (11th January) by the authorities that be.
If they do, Court, one of many Australian Open absentees this year, will not be there to witness it.
Nadal seems to have an easier path through to the finals with Cilic, Sock, Dimitrov and Nick Kyrgios in his half of the draw. It will be held on Margret Court Arena with tennis fans encouraged to attend. "That tends to favour the older more experienced player rather than a player in their teens or early twenties", the study says. As for the men's draw I am going to give Juan Martin del Potro the "dark horse" label. But injury has so often been a problem for the big Argentine. Bencic, who came back from left wrist surgery a year ago is on a 15-match winning streak and showed stunning form in the Hopman Cup last week. If del Potro is fit, then he could go far in Australia, but until all doubts over his conditioning have been proved wrong, he should be viewed as an outsider for the title.
Should Djokovic come through that, he could face France's former world No 6 Gael Monfils, who enters the Australian Open as the recently-crowned Qatar Open champion - a tournament Djokovic has twice won but opted to miss this year to continue his recovery. It's a phrase you'll likely hear over the coming fortnight, but there's no denying he has the qualities to become a multiple Grand Slam champion if, and it's a big if, he can pull it together for a two-week long tournament.