Leclerc was immediately promoted into a race-winning Ferrari seat, a rare move by the Scuderia to advance youth.
Mercedes, though, opted to retain Valtteri Bottas for this season, leaving Russell to remain at Williams on a contract that expires at the end of 2021.
By further comparison, Russell's peers in Alex Albon and Lando Norris both joined F1 alongside the 22-year-old in 2019.
Albon now enjoys a potential race-winning seat at Red Bull, while Norris is sitting comfortably at a McLaren team that is steadily improving.
Bottas, meanwhile, has been on a rolling one-year contract at Mercedes since joining in 2017 but, despite winning seven races, has been unable to consistently challenge team-mate Lewis Hamilton.
Last year, Mercedes motorsport boss Toto Wolff opted to retain Bottas for this season, rather than promote Russell, believing it was "too early" to do so, fearing it would "burn" the Briton in a "high-pressure environment" alongside Hamilton.
Such comments were likely frowned upon by Russell who is itching to compete at the front and who, by his own admission recently, declared himself to be "a little bit jealous" of his mates who are currently enjoying seats in leading teams.
It means Russell will have to 'mend-and-make-do' with another year at Williams and hope he is given his shot with Mercedes in 2021.
While Red Bull and Ferrari have shown they are able to progress their drivers from their own programs, it is an area where Mercedes has failed, which has not gone unnoticed by its rivals.
Referring to the possibility of Sebastian Vettel joining Mercedes, Helmut Marko, the head of Red Bull's driver development program, told Austrian broadcaster ORF: “It’s funny to hear Toto say they are looking at their own young drivers. Until today, no Mercedes junior has made it to the cockpit, but maybe that will change.”
Marko has a point as another reserve in Esteban Ocon was allowed to leave to drive for Renault on a two-year contract, severing all ties to Mercedes.
Nyck de Vries has made the switch to Formula E, rather than face limited options in F1, while Pascal Wehrlein, who ran with Manor in 2016 and Sauber in 2017, was then jettisoned into Formula E, too, competing for Mahindra Racing in 2018 and '19.
Russell remains the most likely option to eventually replace Bottas at Mercedes. Should that be in 2021, you would hope two uncompetitive seasons at Williams do not blunt his racing edge while his rivals establish themselves at the front.
Hamilton may be the all-conquering driver at present, but Bottas has struggled to provide a consistent challenge since his arrival, unlike predecessor Nico Rosberg.
While Mercedes has continued to add to its haul of world titles, Bottas' performances have been deemed to be acceptable, and he continues to be afforded an opportunity.
You would anticipate for Bottas to be retained again for '21, he will be required to go that extra mile in whatever transpires of this term, and push Hamilton as hard as Rosberg did in the year he finally cracked the Briton in 2016 before retiring.
That would leave Russell to see out his contract with Williams. By that stage, the likes of Leclerc would have had three years with Ferrari, similar for Norris with McLaren, and Verstappen five and a half years with Red Bull.
Russell naturally has time on his side, but these are his formative years and you can only hope Mercedes buck their own trend and instead of palming him off elsewhere, they nurture his talent and swiftly promote him into a race seat.
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