Saracens' England internationals will not play a competitive game before the start of the Six Nations.
Players including England captain Owen Farrell, Maro Itoje and the Vunipola brothers will not play a club game until 6 March after the Championship unveiled plans for this season.
English rugby's second tier has not had a game since March due to Covid-19.
Saracens were relegated from the Premiership earlier this year after breaching salary cap rules.
England are due to start their Six Nations campaign against Scotland at Twickenham on 6 February.
It had been suggested that the 2020-21 Championship season would start in January, but it will now not get under way until the weekend of 6 March.
The 12-team league will be split into two conferences with the winners of each playing a two-legged final for the right to earn promotion to the Premiership.
Saracens will be in Conference A and will face Cornish Pirates, Ampthill, Jersey Reds, London Scottish and Hartpury University.
Conference B is made up of Ealing Trailfinders, Coventry, Nottingham, Bedford Blues, Doncaster Knights and Richmond - who come up from National One in place of relegated Yorkshire Carnegie.
Each side will play their opponents in their respective conferences on a home and away basis.
Last season's competition was ended early with Newcastle Falcons promoted to the top flight after the 2019-20 season was decided on a "best playing record formula".
This season clubs are hoping they will be able to stream their fixtures online should they be unable to welcome supporters into their grounds because of Covid-19 restrictions.
"As a result of Championship clubs having little or no income for the last nine months the majority do not have the financial ability to meet the costs of Covid testing required under the elite sport framework," a Rugby Football Union statement read.
"The clubs have chosen not to return to play under adapted laws and the March start date allows time for clubs to gain clarity from Sport England regarding the Sport Winter Survival Package before starting pre-season training.
"All Championship clubs are unanimously behind the intended competition as outlined, but require some weeks of full training, to make squads 'match ready', subsequent to the long absence of competitive rugby."
The RFU also said clubs can continue to arrange pre-season friendlies, as Saracens have already done.