Jos Verstappen has expressed frustration with his son Max's situation at Red Bull, suggesting things need to improve if the teenager is to remain with the team.
Verstappen junior suffered his fourth mechanical failure of the season when an engine problem forced him to retire from fifth in Sunday's Belgian Grand Prix.
Autosport quoted Jos Verstappen as telling Dutch TV channel Ziggo Sport: "I notice about Max that he's very disappointed. It's tough to keep yourself motivated the whole time when things are going like this.
"He's doing very well in qualifying, he's half a second quicker than his team-mate [Daniel Ricciardo] and he's just behind the Ferraris. And then, after seven or eight laps, he's standing at the side of the track again.
"This should not be able to happen, certainly not at a top team."
Jos Verstappen rubbished suggestion that Max's aggressive driving style had contributed to his reliability issues in 2017.
"People are asking that question again if Max is being too tough on his equipment, but that's complete nonsense," he added.
"He can't overdrive, he can't break the material. We all know what it is: it's just the equipment that isn't good enough.
"I think we all need to calm down for a bit and then maybe we need to sit down with each other because this won't last if things keep going like this."