Speaking at Suzuka, Alonso also gave mixed messages about what he really thinks about the dominant Red Bull driver's success.
"He's a fantastic driver and has a fantastic car," said the Ferrari driver.
"It's true he has an advantage in car performance for this year so we'll see how good he is later in his career," added Alonso.
Alonso also hinted that Vettel's superiority this year could have been enhanced by the performance of the driver at the wheel of the other Red Bull.
Alonso, who is close friends with Mark Webber, said of the Australian: "He's lost some of his motivation.
"He's no longer enjoying himself so he decided to retire," he is quoted by La Gazzetta dello Sport.