Red Bull team principal Christian Horner has conceded to being surprised by Mercedes' ability to fight back to the front in 2022 in F1's budget cap era.
The sport introduced a $145million cap for 2021, that was breached by Red Bull, before the limit was reduced by $5million for the past season.
For that campaign, Mercedes got off to a slow start due to fundamental car issues as the W13 battled porpoising and drag-efficiency problems.
Yet consistent development from the Silver Arrows pushed its drivers toward a strong end to the year, with George Russell and Lewis Hamilton securing a one-two finish in Brazil whilst pushing Ferrari close for second in the constructors' standings.
Horner had suggested Mercedes had experienced a "hangover" from the titanic battle for honours in 2021, but speaking to GPFans, he conceded the ability for the Brackley-based outfit to upgrade its challenger had taken him by surprise.
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"Under the budget cap, it has been surprising just the amount of development," said Horner.
"We have had the least crashes and a moderate amount of development.
"But it has certainly been surprising the rate they have developed, particularly in the second half of the year.
"But that is F1. When you consider where they were in Bahrain to where they were at the end of the year, it was a big step."
Backing Mercedes for a resurgence next season, Horner added: "I would expect them to be very strong. They are not going to have the experience of this year.
"Look, they are a very capable team with very capable drivers and we are set for another really competitive season of Formula 1 in 2023."
Additional reporting by Ewan Gale