Christian Horner is convinced Red Bull had the second strongest car at Sunday's Italian Grand Prix but admits the Mercedes was on another level at Monza.

The Red Bulls were second and third fastest in wet qualifying at Monza, but engine penalties saw them shuffled down Sunday's grid to 13th and 16th. Daniel Ricciardo staged an impressive comeback to finish fourth, and was only four seconds off Sebastian Vettel in third after closing on the Ferrari in the final 10 laps.

The power deficit of Red Bull's Renault engine was expected to make Monza one of the team's weakest circuits, but instead Horner believes his team had the edge on Ferrari.

"It is an interesting one," he said, "the cars performed very well here. In Saturday's conditions in the wet, which is always a great equalizer, but again, better than expected, the car performed very strongly in the race today.

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"Analysis will show it was the second strongest car outside of the Mercedes. To start as far behind the Ferraris as we did and only be four seconds behind Sebastian at the finish, was a very encouraging performance.

"Listening to the drivers in the debrief, it is still obvious where we lack in terms of lap time when following our competitors, but the chassis has worked at this particular circuit very well."

Horner said one of the Red Bull's key strengths at Monza was braking, which allowed Ricciardo to pull off an audacious overtaking move on Ferrari's Kimi Raikkonen for fourth place.

"You can see how strong it was on the brakes, particularly with Daniel this weekend. The pass he made on Kimi was from an awfully long way back, so we have found a good balance here."

But asked if Red Bull could have challenged Mercedes had Ricciardo and Max Verstappen not been demoted on the grid, Horner said: "No. Mercedes at this circuit were in a class of their own. Any debate about where the current power hierarchy is in F1 ... this was a Mercedes whitewash."