Scotland internationals Stuart Hogg and Jonny Gray both face between four and six months out injured.
Full-back Hogg, 25, withdrew from the British and Irish Lions tour prematurely with a facial injury, and has also had an underlying shoulder problem operated on.
Lock and Glasgow team-mate Gray, 23, had surgery on a wrist injury after returning from Scotland’s June tour.
Both are doubts for Scotland’s three autumn internationals in November.
The pair will also miss the opening rounds of the Pro12, and the European Champions Cup.
Warriors winger Ratu Tagive is also sidelined for between six and nine months after rupturing his Achilles during pre-season training.
The 26-year-old is on a partnership contract with Currie Chieftains in the top tier of Scotland’s amateur game.
Chiefs head coach Dave Rennie succeeds Gregor Townsend as Warriors boss ahead of the coming season, after his commitments in New Zealand have been fulfilled.