Speaking at the recent Autosport International Show, Chandhok spoke about the recent contract extensions of Verstappen and Ferrari's Charles Leclerc and said that he was confident that only a move to the current champions would take Verstappen away from the Milton Keynes team.
Chandhok, who participated in 11 Grands Prix between 2010 and 2011 for Hispania Racing and Lotus, said also that he thought Verstappen only agreed to such a lengthy contract extension because 'the door was closed' at Mercedes.
"I think Leclerc, first of all, was a no-brainer," Chandhok said. "I think all they needed was to see what he did for one season and make sure he was able to do what they knew but they needed that final confirmation.
"With Verstappen, I think it's interesting because it's a clear sign that he is not going to go to Mercedes. I think that is the only thing that would have taken Max away from Red Bull if there was an opportunity to go to Mercedes.
"I think that now he is confirmed at Red Bull that the message was clearly that the door at Mercedes was closed for him, that's my reading into it."
Chandhok also briefly touched on who he believed would come out on top had Mercedes agreed to partner Verstappen with Lewis Hamilton for any future seasons.
Chandhok noted that it would be enjoyable to see the pair competing against each other in the one team as it would be impossible to predict who could come out on top.
"It is an impossible question to answer," Chandhok added. "I think I would have loved to see it happen, because of that.
"It's the same thing as when Senna went to McLaren in '88 and went up against Prost or when Prost went to McLaren and went up against Lauda.
"You want to see these two giants go up against each other and you would get the answer on the track, but unfortunately that doesn't look like that's going to happen."
Bahrain International Circuit - Winter testing