Red Bull Team Principal Christian Horner expects the threat of its F1 rivals to materialise next season.
The team has enjoyed an unprecedented level of dominance throughout this season having taken victory in all 12 races so far, with eight in a row won by Max Verstappen.
Questions have been raised over whether Red Bull can become the first team in the history of F1 to win every single race in a season.
But Horner is wary of the threat behind in the tight development war, when speaking on the ESPN Unlapped podcast: "Well every week it keeps changing.
"One week it's Ferrari, next week it's Mercedes, McLaren has turned up, and Aston Martin was there at the beginning of the year.
"So every time we look over our shoulder it's somebody else that's there, and that in many respects has helped us, but it's insanely close."
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Horner: Stability in the rules brings teams closer
There will be no significant changes to the cars next year after this campaign saw a number of measures introduced to reduce the porpoising and bouncing that was affecting some teams.
Red Bull also has an aerodynamic testing restriction penalty to serve until October, on top of its reduction for being first in the Constructors' Championship.
Horner expects this to play a major role in their title defence: "With stability in the rules, there will always be convergence.
"If you want close racing, just leave the rules alone and you will always find the teams, they will converge, the cars will converge.
"So I totally expect next year to be a whole different kettle of fish to this year."