Sainz joined McLaren alongside then-rookie Lando Norris in 2019, driving superbly that year to secure sixth place in the drivers' standings, while also claiming his first Formula 1 podium along the way.
The form of the 26-year-old led to Ferrari signing Sainz on a pre-contract agreement as a replacement for Sebastian Vettel before last season had started.
The move now throws up an intriguing pairing for the new campaign which has left Seidl eagerly anticipating the duel.
"It will obviously be a very interesting season because there has been a lot of driver movement and it will be very interesting how he will do against Charles who is very strong," said Seidl.
'With what we have seen in these two years at McLaren, Carlos has everything to become a top driver.
"The way he drives, the way he interacts with the team also outside of the car together with the environment he has around him, I have no doubt he will do a great job there and that he will have success together with Ferrari."
Sainz lost the qualifying battle nine-eight to Norris last year but finished eight points and three positions clear of his team-mate in the drivers' standings as he again ended the year sixth.
Leclerc, in a sub-par Ferrari, scored almost three times the total of Vettel and finished eighth, outperforming the SF1000 to score two podiums in the early races of the year.
Labelling himself a "Formula 1 fan", Seidl confessed he is excited to see how each of the new driver pairings on the grid perform, with only Alfa Romeo and Williams so far fielding unchanged line-ups given Lewis Hamilton has yet to sign a new contract with Mercedes.
“On our side, it will be very interesting to see, with Daniel [Ricciardo] coming in, how Lando will do against Daniel," continued Seidl.
"Seb going to Aston Martin will be very interesting as well so I’m looking forward to this season as well as a Formula 1 fan, which I am.”
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