The highly-rated 20-year old midfielder has fractured a bone in his foot at training on Tuesday morning and will now require surgery to address the problem and is likely to miss up to 10 weeks.
"Jason landed awkwardly in training today and said he felt something go in his foot. There was nothing in it but he limped off and was in some pain," Hearts boss Gary Locke told the club's official website.
"We had him scanned and he's broken the first metatarsal and the bad news is we're looking at him being out for six to 10 weeks.
"We always knew injuries would be a problem for us this season given the size of squad we have but there's nothing we can do about it.
"We'll just have to get on with things. It will give an opportunity for others but we don't have too many options to be fair."
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