The former Rangers striker damaged his knee ligaments against Manchester City at the weekend but if that news is not bad enough, the club have also revealed that the play-off hero has also fractured his tibia - giving the Scotsman a 4-6 month spell on the treatment table.
MacLean's news comes as a massive blow only two days before the start of the season, with Adam Proudlock just resuming training following illness and a septic toe.
Paul Sturrock will also find it hard to call on reserves as Barry Corr and Drew Talbot are both on the sidelines until at least September and Lee Peacock is the only fit striker at the club at the moment.
The one part of reassuring news is that Sturrock is confident of signing a striker before the Stoke clash on Saturday.