Nico Rosberg in '2016 mode' as F1 title hopes fade - Toto Wolff

Rosberg's car incurred a throttle pedal failure early in the Sochi race, forcing him into retirement after he had led the opening few laps and all but ending his 2015 F1 championship challenge.

With team-mate Lewis Hamilton going on to take the chequered flag, Rosberg now trails the Briton by 73 points in the drivers' standings with only 100 to play for.

While Wolff recognises Rosberg is a fighter, he feels the 30-year-old will already start casting one eye towards next season.

"I'm gutted for him, but he's going to recover," said Wolff.

"It takes my head off how he handles the situation, staying calm and trying to recover.

"These boys have been in motor racing all their life. They have won races and lost races, won titles and lost titles.

"The reason why they are here is because they are strong characters and strong personalities.

"As gutted as he might be now, he's realising he's going to switch on to 2016 mode and try to bounce back next year."

Rosberg, however, insists he remains focused on finishing this season as strongly as possible

"I'm not thinking about that [2016]," he said. "I'm just thinking about winning races this year."

As for the title, Rosberg added: "You just have to be realistic now. It's a lot of points.

"But it doesn't change my approach, I'm still pushing to the maximum and committed and going for it mentally.

"It's obviously disappointing because I was looking to close the gap, but I'll go to the next race [in the United States] wanting to win there."

Wolff, meanwhile, has dismissed concerns over Mercedes' rising rate of reliability issues.

Rosberg has now retired in two of the last four races - Italy and Russia - while Hamilton was forced out of the race in Singapore.

Despite such failures undermining Mercedes' previously bulletproof reliability, Wolff said: "I wouldn't be too concerned because obviously mechanical reliability has been good, with Nico's failure a freak.

"If you push the limits of the performance of the car you're going to find out where the limits are."

Hamilton was warned not to use DRS in the closing stages at Sochi due to a rear-wing problem.

"On Lewis' car we had a rear-wing instability which we couldn't identify," Wolff confirmed.

"It was a stalling rear wing out of nowhere, and that was a worry obviously, which got worse in DRS and in traffic.

"We didn't know if it was debris on the rear wing or a problem on the DRS mechanism.

"It wasn't a structural issue, but it was definitely a stalling rear wing, and that is very uncomfortable for a driver."