Ross first suffered the injury a few months ago, but was able to return against Motherwell last month and has played just about every game since then. However, he had to come off towards the end of last week's game against Hearts and missed Saturday's defeat to former club Falkirk. Now, the part-time pundit has decided to call it quits for the rest of the season.
It is a blow to our survival hopes, although not nearly as big a disappointment as it would have been if it had happened last season. Ross was excellent in 2008/09, returning from injury to put in a superb display against the Bairns, but this season he has been pretty poor.
In the last few weeks, rumours have increased that he's already agreed to join Motherwell in the summer, so we may well have seen the last of Jack in a Saints shirt.