Sir Steve Redgrave has urged Great Britain's rowers to lay down a marker for the Olympics in the first race of this weekend's World Cup.
The GB team will be at full strength for the first of three regattas, which starts tomorrow in Belgrade and finishes on Sunday.
Britain are sending 57 athletes - 34 men and 23 women - to Serbia, and with the Olympic squad announced on June 6, rowers will be itching to make an immediate impact.
Redgrave hopes their winter of hard work has paid off, although he is aware that triumphs this weekend are not a precursor to what will happen in London in less than three months' time.
"It will be really quite fun to see how our very successful British team gets on and see what everyone else has been doing," Redgrave said.
"It's not D-Day but it is getting close to it. This is probably one of the biggest days in the calendar, this weekend.
"Obviously if they go out and win, then you can't guarantee winning gold medals in three months but you know you're on target to do that.
"Rowing is a very consistent sport, you need a lot of time to be able to make small adjustments in speed.
"We always have a saying: 'It's what you do during the winter that determines how fast you go in the summer.'
"They've done their winter now but they don't really know where they are.
"They've got their times that they've worked to, they've got a rough idea but actually getting out there against the opposition will give a good marker in a lot of the events."
The men's coxless four - Pete Reed, Andy Triggs Hodge, Tom James and Alex Gregory - will be racing for the first time internationally in Serbia.
And Redgrave believes there will be little room for manoeuvre if they or any of the other British rowers fail this weekend.
"You'll look at the reasons why and there can be all sorts of different reasons," said the 50-year-old. "Hopefully it's not because they haven't done the training over the winter because there's no catching that up.
"You've got to be there or thereabouts at this time.
"Anybody at the races this weekend will go away thinking, 'We were the best at this, but we were bad at this. How can we move forward?"'
After this weekend, the teams will compete in the second World Rowing Cup race, which will take place in Lucerne, Switzerland in three weeks' time, while the final regatta is set be held in Oberschleissheim, Munich mid-June.
"What you find - as long as nobody makes any major mistakes - at the first World Cup race, is everybody improves by the second one, everyone improves by the third one, everyone improves by the Olympic games," said Redgrave.
"Everyone will improve at a similar sort of rate and unless you've made a big mistake, then you can obviously put it right, but they (the regattas) really are the benchmark for what will happen later in the year."
:: Sir Steve Redgrave was speaking as a supporter of the EDF Community Rowing Challenge, which gives aspiring rowers from East London the chance to train with expert coaches and compete at the London 2012 rowing venue, developing valuable life skills in the process.