Rosberg letting title 'slip through his fingers' - Hill
Hamilton took the chequered flag in Spain, and the championship lead in the process, and is yet to be beaten by Mercedes team-mate Rosberg in a straight fight this year. Hill thinks Rosberg's opportunity to seriously challenge Hamilton may have already passed with a decisive psychological blow over the last three races.
"Nico is going to have to beat him on the track," he said. "You can get up to games and put pressure on people, but unless you deliver and get your car in front and keep it there until the end of the race, it's all meaningless.
"Nico had two opportunities to beat Lewis, in Bahrain and Spain, but he let them slip through his fingers. That might already be too much to recover from. You look at Lewis and you think he's good, but he's not unbeatable. But you look at Nico and you think he's going to have to find that last 2% or 3% to be able to put pressure on Lewis.
"I thought it was crucial in Spain to be honest. I thought if Nico had summoned up something he had never summoned up before in his life and beaten Lewis, then we would have had a championship battle. After a bit it just starts to grind you down if you're not careful and it starts to become a question of not believing it's possible to beat the guy. That would be the end of that if that happens.
"It must have taken a lot out of Nico in Spain to have led all the way through the sessions and just be pipped in qualifying and just be beat in the race. I'm sure he gave what he thought was everything he had, but you just have to give what you couldn't believe was possible to win."
Hill thinks Hamilton looks like a new man this year but is certain he has another level to reach this season.
"Up until this season, it always looked like Lewis' focus could go at any time," Hill added. "He now seems to have the demeanour of someone who is totally content. I do wonder if he is just cruising. I think he has another gear. He is so focused on the job, I think he will be almost impossible to beat."