Andreas Seidl has admitted his opposition to the trend for longer Formula 1 calendars made possible by the likely introduction of Imola-like two-day race weekends.

Just as news of the unprecedentedly long 2021 calendar featuring 23 races broke, Formula 1 descended on the much-loved former San Marino GP venue Imola for a novel two-day race weekend experiment.

McLaren boss Seidl is worried about the trend.

"I'm not a fan of a calendar of 23 races. I think 20 is really enough," he said.

It is believed the draft 23-race schedule is almost identical to the original 2020 calendar, except that it features a new race in Saudi Arabia.

That would mean highly popular former F1 circuits drafted in at short notice amid the corona crisis this year - such as Mugello, Imola, Portimao and Turkey - will not be returning in 2021.

"What I would like better is a rotation principle, which means we could keep visiting different places while still building new venues," Seidl said.

McLaren driver Carlos Sainz agrees with his boss.

"I don't like the plan to hold more two-day events," he said at Imola.

"We're a circus and when the circus is in town it should make an impression on the fans. We won't do that if we're only there for two days and then - whoosh - we're gone again."

Sainz says he likes the sound of Seidl's idea that new circuits and more historic circuits share the Formula 1 calendar by annually rotating or alternating.

"This year we have learned that there are tracks on which Formula 1 can offer a great show. This does not apply to all the circuits on the calendar," he said.

"So I think it would be good if we took turns like that," said the Spanish driver. "We should sprinkle tracks like Imola, Portimao and Mugello in there every few years to offer more variation.

"I would prefer that to more and more races over fewer days."