Team New Zealand and the British outfit led by multiple Olympic champion Ben Ainslie could both have their plans upset by the absence of key sailors preparing for the Rio Games when the fourth Americas Cup World Series event of 2016 gets underway in Portsmouth, on England's south coast, this weekend. Series leader Emirates Team New Zealand, with a 10-point lead over Ainslie's British team Landrover BAR, will be missing star helmsman Pete Burling who has been central to their success this season. Meanwhile his Olympic 49er teammate Blair Tuke will also be absent as the pair prepare for Rio. It will mean a new set up on board, with only one of the five crew racing in their regular positions. "We have always known Peter and Blair have had the Olympics to focus on entirely from now and of course we want to do everything in our power to support them towards winning that gold medal," said new Kiwi helmsman Glenn Ashby. "So we will have to do the best we possibly can to try to maintain our lead over an ever increasingly competitive fleet," he added. "If we can come away from Portsmouth still within shot of the top of the leaderboard, we will be happy." Nathan Outteridge, the Australian who will compete against Burling and Tuke in the 49er class in Rio, is replaced by Italian Francesco Bruni as helmsman on Artemis Racing, winners of the last event in Chicago. Lying second in the overall ACWS rankings after three events, Landrover BAR is now clear favorite to retain the Portsmouth crown it won last year though Giles Scott, regarded as a gold medal certainty in Rio, will now be replaced by Ed Powys. Ainslie, a four-time Olympic champion, is bidding to become the first man to skipper a British boat to America's Cup glory. This weekend's two days of racing will see him attempt to accrue points in the ACWS, which features the spectacular AC45 foiled catamarans. That will determine the starting points score of the teams in the America's Cup qualifiers in 2017. Five challengers are vying for the chance to take on America's Cup holders Team USA in the America's Cup final in Bermuda in 11 months' time. Ainslie's team has its headquarters in Portsmouth and is at the core of a multi-million pound business, funded by some of the country's wealthiest businessmen to bring the America's Cup, regarded as sailing's holy grail, to Britain for the first time. Six teams will take to the Solent, where the America's Cup was famously first contested in 1851, is a series of six scheduled races with points awarded Saturday and double points Sunday. The course has been shortened to keep the spectacular ‘flying' AC45 catamarans nearer to the shore, with crowds likely to witness the boats flying across the water on their foils at speeds of more than 30 knots. "The guys are really fired up for this event," said Ainslie. "It's the last time we get to race on home waters before next year's America's Cup so it's really important for us to put on a good show in front of our home crowd. "We really want to get some of those bonus points going into the America's Cup next year."