Sebastian Vettel will not give up on catching Lewis Hamilton - Nico Rosberg

Lewis Hamilton (left) leads Sebastian Vettel by 59 points in the World Championship

Ferrari's Sebastian Vettel will not give up on catching Lewis Hamilton in the drivers' standings, according to retired world champion Nico Rosberg.

With four races to go, Vettel is 59 points behind Mercedes driver Hamilton with a maximum of 100 still on offer.

Rosberg says his fellow German is a "fighter" but needs a "miracle" if he is to win a fifth world title this season.

"Ferrari always come back strong," Rosberg, 32, told BBC Sport.

"It's so difficult for Sebastian now. Lewis has such momentum, everything is going in his direction.

"Sebastian needs a miracle to come back but he's a fighter and he won't give up. It will remain interesting so let's see how far he can take it."

Meanwhile, Rosberg says Polish driver Robert Kubica is being evaluated by Williams over whether he can make a return to Formula 1.

Kubica, 32, has not raced in F1 since a rally accident in 2011 left him with only partial movement in his right arm.

Rosberg is part of the former BMW Sauber and Renault driver's management team.

"Williams is evaluating him so we need to be patient," he said.

"In my 20 years of racing, the fastest guys I saw were Hamilton and Kubica, so I know how fast he can be.

"I am exploring and enjoying this management side of it - it's different doing it for someone else. I was my own manager, but this is another good way to stay connected to the sport."