David Wagner has warned his returning Norwich City players they will 'suffer' in pre-season to prepare for the Championship kick-off.

The German and his coaching staff have mapped out a series of triple daily training sessions to reach the physical levels Wagner demands.

Norwich’s internationals, and the likes of summer signings Shane Duffy and Jack Stacey, should all be back in the fold by the start of next week at Colney.

“There will be some days where we suffer, but we only can change your borderline if you are prepared to push that borderline,” said the City head coach. “This means we have a lot of triple sessions planned where we train at 8am, 11am and 4pm. But it's pre-season.

"I said to the lads on day one when we all came back that pre-season is never the most enjoyable part of the job, but it is a part of it.

“There are harder jobs than being a football player on this planet as well. But if they stay healthy, and this is the most important thing for me, then these six weeks they get on the grass under their belt means they are on a level I can close my eyes, and know they can run like hell.”

Norwich begin their pre-season friendly schedule at non league Barnet next week. Max Aarons will hope to still be away with England’s Under-21s as the European Championships reach the later stages.

Aarons could be involved later on Wednesday in the Young Lions' final group game against holders Germany, although Lee Carsley’s squad have already sealed top spot and a Sunday quarter-final.

The City full back is expected to leave this summer, while fellow young defender Andrew Omobamidele and winger Milot Rashica are also touted with exits, but Wagner is clear departures will only be on the club’s terms.

“The good thing is we don't have to sell. I think there's always a big, big difference. I worked in environments where you were under huge pressure to sell and this can cause some problems,” he said, speaking at BBC Radio Norfolk hosted fans’ forum. “We are open to sell if the right offers are on the table for the right player.

"We're always very honest to the players as well, what I think is crucial, and then we will see what the window brings, but I expect some more ins and outs.

“Everybody's aware how our football club is set up to produce a talent, turn that into quality, and then to sell at the right moment and re-invest that in improving infrastructure or back into the squad.

"This is a big part of our work, and my work as well. That is why it is important to have great facilities and a great academy to produce players who, with time, can transfer that talent into quality performances.

“There is no club on the planet who will not change their squad in some way. From a relationship point of view it is not nice, if you have worked with them for any length of time. But we know this business and this industry.”