Olympic rowing champion Duncan Free's hopes of a fifth Games campaign goes on the line this weekend when he makes his international return to competition in Switzerland.
Free will make his comeback from two shattering leg and rib injuries, that combined to derail his initial London Games plans, in the men's pair with Fergus Pragnell in Lucerne at World Cup 2.
The 38-year-old, who teamed with Drew Ginn to win gold in the pair at the Beijing Olympics, had originally been seen as a key member of the new-model Oarsome Foursome until injuries struck.
He and Pragnell must now outperform compatriots James Marburg and Brodie Buckland in Lucerne to gain selection as Australia's men's pair for London.
Marburg and former USA rower Buckland rank as favourites for the boat following impressive trialling times and more time together as a crew after they both missed spots in the men's eight in late March.
Pragnell was only confirmed as Free's partner a week ago following a last-ditch selection trial at Penrith Lakes against Tom Larkins, who will also row at World Cup 2 with veteran Nick Hudson for race practice.
A clearly superior result by one of the duelling crews is set to decide the boat for London and failure by Free could mean he'll remain with the 47-strong Olympic team as a well-credentialed reserve.
Heats at the World Cup regatta begin on Friday night (AEST) and a total of 13 Australian boats will be in action over the weekend, with finals scheduled for Sunday night.
Ginn's new men's four - including Josh Dunkley-Smith, James Chapman and Will Lockwood - will also get an important gauge of their credentials against defending world and Olympic champions Great Britain, who won World Cup 1 in Belgrade.
Australia's world champion men's lightweight fours crew is intact but the highly-ranked quad sculls crew is without injured stroke Dan Noonan (ribs), replaced by Jared Bidwell.
Although the regatta is the first in a two-month build-up to the Olympics, there's great interest in how the Australian women's quad scull crew performs.
An unknown quantity, the new crew of Kerry Hore, Pippa Savage, Pauline Frasca and Dana Faletic have been producing impressive times in practice to give hope they can challenge Germany and USA.