Spaniard Alonso is obviously frustrated amid the current McLaren-Honda situation, and his old friend Mark Webber thinks it possible that he will quit mid-season.
There are even reports in Spain that Alonso could leave the British team this year to return to Renault.
"We are getting enormous pressure from the team and from the drivers," Honda F1 chief Yusuke Hasegawa admitted, according to German news agency DPA.
Yet amid that high pressure, Massa does not think Alonso will walk away.
"I think the first thing to understand is that he has a contract," he told Brazilian broadcaster Sportv.
"If he leaves now, he'll be stuck until next year, and for what? We also can't forget that he has a huge contract. So he will stay there and fulfil it, although it's true that anything can happen.
"But if he's thinking of moving to a competitive team, that's not for this year. Stop in the middle? I don't think so, but as I said, nothing is impossible."
McLaren go into next weekend's Chinese Grand Prix pointless, Stoffel Vandoorne and Alonso having placed 13th and 14th respectively in Melbourne.