MELBOURNE (REUTERS) - The gulf between Australian tennis great Rod Laver and the nation's brightest hope Bernard Tomic has been starkly highlighted this week with bouquets flowing in one direction and brickbats the other.

The 75-year-old Laver, the only men's player to win two calendar grand slam titles, has been warmly welcomed Down Under after making the journey from his California home to launch his autobiography Rod Laver: A Memoir.

Tomic, ranked 52nd in the world, has been panned on social media for retiring when 1-4 down in the deciding set of a first-round encounter in Spain against Russian journeyman Mikhail Youzhny on Tuesday.

Coming the day after his 21st birthday, Tomic's withdrawal from the Valencia Open match was due to a headache, according to local media, and continued a pattern of late-season fadeouts that proved controversial last year.

A season that began with promise last year ended with the Germany-born player getting booted out of Australia's David Cup team for a perceived paucity of commitment.

Tomic, touted a future top 10 player, put behind last year's troubles with a bright start to the season but was soon plunged into controversy by his father's conviction in a Spanish court for assaulting his former hitting partner.

Tomic rallied with a fourth-round appearance at Wimbledon but has failed to pass the second round in his last eight tournaments.

However legitimate his reasons for pulling out in Valencia, the news has been greeted with scepticism Down Under, where tennis fans have long hoped for Tomic to take the mantle from ageing two-time grand slam winner Lleyton Hewitt.

Laver said Tomic would be doing himself a disservice by not playing every game as if it were his last. "I know there are some down-times and I think when he looks back at things in five, 10 years from now, he may be disappointed with himself," Laver told reporters at his book launch at Melbourne Park today.