"He spun off in the fourth round in a very clumsy way and that is not the first time this year that the German is making mistakes," Doornbos said in his Ziggo Sport column. "He also ran against Stroll once again and ended up with it looks ashamed on his jaws a lap behind his winning teammate.
"Sebastian Vettel will be under extremely high pressure if this continues if his younger teammate drives him around. Either Vettel will be relentlessly fast in the coming races or I think they will slowly start thinking about a successor for Ferrari the German and then Daniel Ricciardo could be a possible party."
Vettel will desperately hope to impress in Singapore and get back on the podium to prove his worth.