Mercedes chief Toto Wolff has admitted the team's rivals have started to close the gap on the frontrunners in F1.
The Silver Arrows have already wrapped up the Constructors' Championship this season, with Nico Rosberg and Lewis Hamilton the only two men capable of winning the World Drivers' Championship.
However Red Bull have shown plenty of promise with Daniel Ricciardo and Max Verstappen behind the wheel, while Ferrari have been steady through the season.
Wolff has conceded it was more difficult to win the Constructors' this time around and expects the gap to be even closer next season.
He was quoted by Plant F1, saying: "It wasn’t as dominant of a season as it was last year, and for me it’s just the fact of diminishing returns with the stable regulation.
"It’s what we always said, leave the regulations and leave the rules alone and the performance gap is going to shrink and eventually we’re going to have some good racing."