The Jambos defender had to be stretchered off during Sunday’s 4-0 defeat at Celtic Park after suffering a suspected ruptured Achilles.
The worst-case scenario would see the Scotland Under-21 cap ruled out for a year.
Cathro admits that would be a bitter blow for a player who has been tipped as a future candidate for Gordon Strachan’s full international squad.
He said: “We are still going through the consultations and things but it doesn’t look like it’s a great situation.
“We’re still checking up some things but he has an Achilles problem for sure.
“Will he miss the rest of the season? That’s a possibility.
“The situation with John is one where his career will flourish, irrespective of what has happened.
“He is a very talented, a very motivated young player. He also has a very strong mind, he’s had to deal with some bits and pieces of flak and frustration, even from his time at Dundee United.
“That was a bit of a challenge for him but he is a strong young man having dealt with that.
“We need to give him time to address exactly what the situation is. Hopefully it’s not that bad.”