Sir Ben Ainslie is Oracle Team USA's high-risk choice to rescue their America's Cup defence They played their postponement card on Tuesday and called time on racing after losing race five, then attended the press conference that evening without Kostecki giving weight to rumours of a shake-up. On Wednesday, Ainslie was seen out training, wearing Kostecki's body armour which was a precursor to the announcement that the switch had been made. "It's a tough decision to make, but I'm happy to step up and do what's best for the team," confirmed the 36-year-old Ainslie who said on Tuesday he believed Oracle could still win the America's Cup if they could change its momentum. I have a huge amount of respect for JK and really appreciate his support in making the transition. Russell Coutts, Oracle CEO, agreed it was a high-risk option but said they were confident that Ainslie would make a difference. "You've got to remember, changing personnel at a time like this has never worked in the past so we've got to be cautious about making a change like that," he said. We wouldn't be thinking about it unless it had a really good chance at working. Oracle Team USA made no other changes to their 11-strong crew but went into races six and seven against Emirates Team New Zealand with a deficit of five points needing a miracle to turn things round. They have minus one point, having been docked two points before the cup started on Saturday for their part in a catastrophic cheating scandal. The Kiwis were four up needing just five more points to wrest the cup away from the Americans who now need 11 victories to retain their crown. A win for Oracle Team USA would not just be good news for the Americans but also for Britain since Ainslie signed up for this campaign as part of a longer term plan to raise his own challenge for the 35th America's Cup with the aim of winning it for Britain for the first time. The first America's Cup took place in 1851 as a race around the Isle of Wight and was won by the Americans. Every attempt to win it back since then has proved unsuccessful but giving the Americans a chance of a win would raise hopes that Ainslie could do it next time for Britain and almost guarantee him the millions of pounds of funding he would need for a British campaign. Win or lose, he has everything to gain.