Both members of Town's playing staff suffered ligament damage in the closing stages of the 2008/9 Coca-Cola Championship season, and will therefore likely join pre-season training after the rest of Town's squad.
Confirming the news to the Official Club Website, Town Physio Matt Byard said of Thatcher: "Ben is three weeks into his injury. He's on crutches and the knee is immobilized.
"He will be seeing a specialist soon and then hopefully he will begin swimming and cycling. His injury is going to take about three months before he is back fully so he going to have a bit more of an individual style start to pre-season but I would envisage him being back playing football again by the middle of July.
In relation to Skipper McAuley, Byard added: "Gareth has a similar injury to Ben although not as severe but again it's likely to take around eight to 10 weeks to resolve.
"He will start some rehab work in June but I would look at him maybe being a week or so behind the rest of the lads when the pre-season programme gets underway."
Click here to see a player by player stats for the 2008/9 Coca-Cola Championship season.