I'd imagine it will be something like this in terms of start of pre-season for the different groups:
Saturday 6th July: Grabara, Kelleher, Clyne, Hoever, Adam Lewis, Matip, Van den Berg, Nat Phillips, Rhys Williams, Fabinho, Milner, Ejaria, Herbie Kane, Curtis Jones, Woodburn, Lallana, Ox, Kent, Wilson, Brewster, Paul Glatzel, Bobby Duncan
Friday 12th July: Henderson, Gomez, Trent, van Dijk, Wijnaldum, Origi, Mignolet, Lovren, Shaqiri, Robertson
Monday 29th July: Alisson, Firmino
Sometime in August: Salah, Mane, Keita