Toto Wolff said it was a "bittersweet" end to the drivers' championship because he feels Mercedes let Nico Rosberg down.

Lewis Hamilton won the title with victory in the Abu Dhabi Grand Prix, but Rosberg's hopes of overturning his team-mate's 17-point advantage were ended with an ERS failure which saw him limp home 14th. Wolff said he was relieved the title had been decided but was disappointed not to give Rosberg a car capable of challenging in the final race.

"First of all it's a relief now and that has really kicked in in the last hour," Wolff said. "Because even though we had won the championship, we knew that we had won the drivers' championship before, we knew that the difficulty ... it was going to be a challenge staying neutral and balancing out between the drivers. For us it was a particular challenge, so now that is over it is a relief.

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"But then there is also a bittersweet feeling left. Lewis Hamilton won 11 races, he deserved to be world champion. He had a really incredible season, he had many downs and many ups and at the end he's a worthy world champion.

"The bitter part is we worked so hard in such a diligent way to make the car reliable to enable the boys to fight it out on track and that we had the problem on Nico's car is something that gives us the bitter taste and I feel that we let him down a bit. Then in hindsight you can say from the rational point of view it was already difficult to really make it after he had not a perfect start. So the good feeling is we are world champions and Lewis Hamilton is a world champion and that's great."

However, Wolff conceded that it would have been an even worse feeling for the team if reliability issues had robbed Hamilton of victory and the title when he was leading.

"Nico not finishing for us is a personal drama because we expect to give them cars which make it to the end. Lewis not finishing, being in the lead of the championship and being in the lead of the race would have been an even bigger drama. Nevertheless, that doesn't make it any more good to see Nico's car break down."