"I told him: 'There are 50 engineers working on this engine and they can't sort it out," Marko said in an interview with the BBC.
"'You're a top driver, it's up to you. You have to do it.'
"If he can't sort out the car, the easiest thing is the driver. He has to raise his game."
The Red Bull advisor also admitted that the Bulls considered signing Lewis Hamilton when he went on the market after his six years with McLaren.
In the end, the team felt that Vettel and Hamilton would make for a difficult partnership.
"We were considering it, but we thought it wouldn't work," said Marko. "To be successful, you need a certain amount of harmony."