ALICANTE, Spain, April 3 - The enthralling, absorbing Leg 5 of the Volvo Ocean Race will come to a climax on Sunday when any one of four boats could claim victory in Itaja��_ after three weeks and 6,776 nautical miles (nm) full of thrills and spills. The stage has more than lived up to its long-standing reputation as the roughest and toughest of the entire nine-month marathon and a real boat-breaker. It has seen the retirement of Dongfeng Race Team (Charles Caudrelier/FRA) following a mast breakage early on Monday, shortly before the crew was due to round Cape Horn, and at least three episodes when boats crashed to their sides in Chinese gybes. Much more surprisingly, has been the incredibly tight racing at the head of the fleet and by 0940 UTC on Friday, it was still far too close to call with under 575nm to go. Overnight, there were no less than three lead changes with Abu Dhabi Ocean Racing (Ian Walker/GBR) emerging in front after both Team Alvimedica (Charlie Enright/USA) and MAPFRE (Iker Mart��_nez/ESP) had briefly taken over at the head of the fleet (see panel above). Team Brunel (Bouwe Bekking/NED) were by no means out of contention, either, just 17.3nm behind the leaders. Behind them, Team SCA (Sam Davies/GBR) were doggedly ploughing through the south Atlantic, just over 700nm behind the leading pack with 1,277nm left to the finish in Itaja��_ (0940 UTC). "It's like being in a washing machine," said Onboard Reporter, Anna-Lena Elled (SWE). Victory would put Abu Dhabi Ocean Racing in a strong position after joint leaders, Dongfeng Race Team, were forced to abandon the leg and continue under motor and sail to Itaja��_ for a new mast fit. But the overall race would be very far from over and, in any case, MAPFRE, winners of Leg 4, were clearly in no mood to concede a metre to their Emirati rivals. "We have spent a crazy night, I hope the last like it in this leg," wrote skipper Iker Mart��_nez in a blog from his boat on Friday. "The wind increased and veered so much that we ended up sailing at 20 knots against the waves, bouncing around. "It seemed that everything was going to break. A porthole flew off the boat and the only safe place was the bunk, squeezed against the hull because otherwise, as the boat jumped, you could be thrown anywhere. "We would have liked to get more miles out of the situation, but it has not been easy to steer. "The bowmen could have been washed overboard any time so we've been forced to put safety first. This is the third time it's been like this since the leg started, yet we've not had these kind of conditions before that since we'd left Alicante." He now expects a real sprint to the finish into south-east Brazil. "The dice has rolled. Now it's down to a high-speed race for the last few miles, while we wait for the wind to veer starboard (right) again." The leading four are expected to finish on Sunday afternoon/evening according to the latest estimates from Race Control.