Tasmanian Tigers vice-captain Dan Marsh will be sidelined until Christmas after dislocating his shoulder in a pre-season training session.

Coach Tim Coyle said the injury was caused by a "freakish accident", when wicketkeeper Michael Dighton landed on Marsh after taking a tumble during a fitness session on Monday.

Scans on Tuesday revealed a separation of the left AC joint and Marsh has already undergone surgery to stabilise the injury.

"He's very down," Coyle told reporters.

"It's unbelievable to him that it's happened. I think he just wants to get in and get it fixed and then see how it comes back."

Coyle said medical staff were "quite optimistic" about Marsh's playing future but the latest injury left the Tigers without four of last year's ING Cup-winning team.

Run machine Michael Bevan won't be back for a few games after undergoing knee surgery in the off season.

Pace bowler Brett Geeves and all-rounder Luke Butterworth are also out with injuries.

"That's a big hole but ... it gives someone else the opportunity," Coyle said.

"We've just got to face that challenge.

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