If some of the Big Four are showing signs of peaking - Rafael Nadal's knees, Roger Federer is now 31 - it may be time for some of the younger brigade to announce their intentions of sitting at the top table with their appearance at the Australian Open. Some of the best chances in the tournament (not necessarily to win it but maybe to enjoy an extended run and present their credentials) are:

Milos Raonic
(Canada, world ranking 15)
Like Juan Martin del Potro, he's big (1.96m) with lightning serves. Was beaten by Lleyton Hewitt in a warm-up tournament recently and can be vulnerable to a swift-moving, dogged returner. Needs to lift his all-round game and is yet to perform well at a major, in spite of his promise and obvious weaponry.

Bernard Tomic
(Australia, world ranking 64)
Undoubted talent but seems to have problems off the court, with a colourful tennis parent and a questionable attitude at times. However, he demonstrated his ability with a run at Wimbledon two years ago and he loves the limelight and the pressure that goes on at his home tournament. Still only 20, so has time on his side and is a genuine touch player. Beat Novak Djokovic in the Hopman Cup last week.

Ryan Harrison
(US, world ranking 68)
Another 20-year-old, with a fiery temperament that gets the better of him at times. The search for a US tennis prodigy has been fruitless thus far and often damaging to those in the frame but Harrison has genuine ability if he can master that hot-headedness. Drawn to meet Djokovic early, however.


Alexandr Dolgopolov
(Ukraine, world ranking 20)
Only 24, the unusual quick-fire, high-spin, varied-pace style of the Ukrainian makes him difficult, as does his all-court running and fetching. Likes this tournament, making it to the quarter-finals in 2011 and the fourth round of the US Open the same year - his best so far. Has never beaten one of the Big Four but has pushed Djokovic hard in their two clashes.

Grigor Dimitrov
(Bulgaria, world ranking 41)
Has been called the new Federer enough times to make him well and truly sick of the title but the 21-year-old is a similarly elegant player on the way up. Lost to Andy Murray in the final of the Brisbane International last week.