Finn Hakkinen, the now-retired 1998 and 1999 title winner, is unimpressed.
"For Vettel it's an unpleasant surprise that Ricciardo is beating him," he said, "but instructions from the team have to be followed.
"Even last year I was surprised by Vettel's behaviour towards his team, and now it goes on," Hakkinen, obviously referring to the 'Multi-21' scandal involving Mark Webber in 2013, told Hermes in an interview.
"Behaving like that will, sooner or later, hurt him. Maybe he (Vettel) is planning to change teams, but right now he's not behaving in the right way," he added.
Hakkinen also commented on Ferrari's shock management switch, after Stefano Domenicali was suddenly replaced as team boss by the mainly unknown Marco Mattiacci.
"Stefano is a friend," Hakkinen said, "but sometimes change is necessary.
"It's difficult to say whether Ferrari has made the right decision, but when large companies are not getting results, heads can roll."
When asked about Mattiacci, the former McLaren driver said: "Only time will tell how he will go, but if you don't have much experience in formula one, it will be difficult to get straight down to work."