Sato’s manager critical of Red Bull
The Japanese driver tested several times over the winter for the energy drink company's Ferrari-powered secondary team Toro Rosso, but the race seat ultimately fell to incumbent Sebastien Bourdais, with 32-year-old Sato also failing to agree a deal as reserve driver.
At the end of the saga, Sato's manager Andrew Gilbert-Scott is unimpressed.
"What they said and what happened often did not match up," he is quoted as saying by the Swiss specialist publication Motorsport Aktuell.
"I tried to arrange a discussion with Dietrich Mateschitz, but he didn't want it," Gilbert-Scott added. "It was always 'get sponsors, get sponsors!'.
"Everything was confusing, not open, disappointing."
Gilbert-Scott also alluded to the link between Bourdais' appointment and the surname of the Frenchman's manager Nicolas Todt, whose father Jean headed the Ferrari team until 2007.
He is now exploring options for Sato, who contested 93 grands prix between 2002 and last year, in America.
"We are looking at IRL or sports car projects in the United States," Gilbert-Scott revealed.