A decade after his father predicted he could have won "10 to 15 grand slams" by now, Bernard Tomic is in rankings freefall and in danger of spiralling out of the world's top 200.

Tomic turns 27 on Monday but must be wishing he could wind back the clock to his heady days as a prodigiously talented junior.

Bernard Tomic will turn 27 on Monday. Credit:EPA

At 15, Tomic won the Australian Open boys' singles title and it was after he added the US Open junior crown to his collection a year later that John Tomic urged Tennis Australia to break the bank for his son.

John Tomic wanted TA to hire super-coach Darren Cahill to ensure Bernard could maximise his rare potential.