The Scotland U21 international broke a bone in his foot during training on Tuesday morning and will have surgery next week.
Hearts manager Gary Locke told the club’s official website: “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.
“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.”