Former Stars & Stripes helmsman Ken Read believes the Prada Cup final is "too close to call".
Luna Rossa and INEOS Team UK begin the best of 13 race challenger finale on Saturday, with where the winner will earn the right to face Team New Zealand for the America's Cup next month.
There has been much conjecture among the sailing world about which team is favourite to challenge for 'The Auld Mug' with the Brits having dominated the round-robin, but the Italians have the experience of two-time winner Jimmy Spithill at the helm.
Both crews have been quick to play the underdog tag ahead of Saturday's first race, and Read says that is likely because neither challenger is convinced they have the best package.
The American, who steered Dennis Connor's challenge in 2000 and 2003, tells the AM Show he expects the match-up to go the distance.
"I think this is too close to call," Read says.
"Anyone who says they know who is going to win is lying
"We don't know what boats will show up. What little bits and pieces have they put on the boats to make them go faster
"We have two really aggressive teams who sail very well - I don't see a whole lot of weaknesses and we are hoping for along series
"This could go on for a couple of weeks and I suspect it could go down to the final race - it wouldn't surprise me."
And Read believes whoever emerges victorious will hold an early advantage over the defenders come the America's Cup proper.
The defenders haven't raced competitively for two months, leaving the challenger battle-hardened and "match fit" for the regatta's culmination.
"They will be match fit - there is nothing like that.
"Team NZ does their own training races but there is nothing like being match fit
You get into the starting box and the bullets start flying for real and it's a different game. The challengers will have an advantage - no doubt about that."
Join us on Saturday for live updates of the Luna Rossa v Team UK America's Cup challenger final.
