Garbett was not involved in squad photos for this season and has not been given a squad number:
https://www.instagram.com/p/DdZkD0vjL4E/?stkn=ZnlrbDNyeGxxdnU5
However, Posh chairman quoted in an interview with ‘Peterborough Telegraph’ yesterday:
"Matty Garbett is on a two-week training course somewhere near St George’s Park which is really intense. He should be back with us for the last two days of September and then he should be fit to go the following week.”
https://www.peterboroughtoday.co.uk/sport/football/peterborough-united/chairman-wants-his-clubs-aura-back-good-garbett-update-and-rules-have-killed-posh-ahead-of-stockport-county-trip-9093876