Leicester Tigers head coach Geordan Murphy has said Premiership players will need two months to properly prepare for a full return to action.
Premiership Rugby hope to restart the season in July, with clubs waiting for the go-ahead from the rugby union authorities before resuming training amid the coronavirus pandemic.
Murphy said union's physicality means players must "ramp up" training.
"There has to be a slow, graded return," he told BBC Radio Leicester.
"That would be a minimum of eight weeks, which is what we're planning. It will be decided though by the Rugby Football Union and Rugby Players Association , so I don't know where we will end up."
Murphy takes over as director of rugby when Steve Borthwick officially becomes head coach on 1 July. Tigers were 11th in the Premiership, the same position they finished in 2018-19, when the season was suspended on 16 March.
But the uncertainty surrounding when the sport will return, how and when this season will be completed and the affect it will have on player contracts is adding further confusion.
"The reality is that we'll be back as soon as we can in front of crowds, and we expect that our early games will be played behind closed doors," Murphy added. "It will be unusual to play matches without crowds, but the players will just want to be back on the field and getting rugby back under their belts.
"Our contracts are starting on 1 July, and that's what we are working towards, fulfilling those contracts. If someone is out of contract, they will join a new club, and we are expecting new players to arrive to start their jobs.
"Having said that, there are a lot of unknowns in that, we need to speak to the RFU and RPA. We are still working towards a start date, and when we know, we will make those assessments."
Lam and Jordan's Last Dance
Bristol Bears director of rugby Pat Lam has said there is "no excuse" for players being rusty when they return to training and says meticulous plans are in place to ensure they are as ready as they can be.
And he said his players have been helped to stay motivated by taking inspiration from basketball legend Michael Jordan while in lockdown.
The much-acclaimed Netflix series 'The Last Dance' chronicles Jordan's stellar career - and in particular his final season with the Chicago Bulls.
"I said to the boys I am so going to be so excited to see your skills because skills need time and prep and you've got time," Lam told BBC Sport.
"I am expecting better line-out throwers, better goal kickers and better passers and a lot of variety. They are sending videos to show me what they are doing.
"There is no excuse at all to come back and your skills are rusty when you have had all this time, which is what you need as Michael Jordan demonstrated on Last Dance. I couldn't have thought of a better series to put on TV. It just lifted everybody who realised, 'ok I have to go to that level'."
Lam's side were third in the table, seven points behind leaders Exeter Chiefs when the season was halted.
Bristol cover every base
"What we've done in our planning is to look at every single scenario," Lam added.
"I would imagine it would be very similar to the football where we come in in small groups and maintain social distancing.
"As an example, one of the plans we have in place - and all the departments have looked at it - is that there would be a one-way system coming in. Guys would be scheduled for a certain time.
"So five guys might come in and in the hour that they are allowed to train they might start off with their first bit where they come into an area where they do warm-ups and their stretches so they are already changed and ready to go.
"They come onto the field and as coaches we are prepared for whether they stay two metres apart, they all have a rugby ball and whether they are allowed to pass the ball to each other or not and we have a variation of drills depending on that."
Lam said the sessions would then most likely involve some conditioning work followed by weights sessions before heading off home while the "next set of guys come in and we wipe down all the equipment".
"We are waiting to be guided as to what those regulations are," Lam added. "But we went from worst-case scenario that this is what you have to do so we make sure we planned so that it doesn't get hit on us and we go 'what are we going to do now?'.
"There are probably about five to eight variations building up to everyone coming back to training. That's why I am really proud of our staff; we have some quality people.
"I asked the questions. They went around did their research and talked to different sports, different people in the government and got medical advice and brought it together so we are ready to go whatever happens.
"We are ready to go."