"You can go from literally wanting to kill a guy on the water to becoming pretty good mates with him after."
Spithill's Team USA and Barker's Japanese syndicate formed a working relationship in the 2017 campaign in Bermuda, and the two will again find themselves as foes when they lead Luna Rossa and American Magic respectively to New Zealand in 2021.
Spithill was confident he could upset New Zealand fans again as he looked to repeat the feat of Russell Coutts' Alinghi syndicate who won the America's Cup in Auckland in 2003.
"Personally I wouldn't be here and I don't think the team would be here if they didn't think they had a shot at winning."
Interest has been high in the 2021 regatta ever since Team NZ announced the class rule for the event. The radical 75-foot monohull design expected to reach high speeds and bring another level of excitement to the racing on the water.
However there have been some critics of the choice of vessel to sail and when asked if he was a fan or not, Spithill said he didn't have the right to an opinion on it.
"Whether I'm a fan or not, it's not my choice," he said.
"It's simple in the America's Cup; if you want to decide what the next event is, where it's raced, boats you're sailing in, how the event's shaped you have to win it."