The 27-year-old Scotland international last night underwent surgery to repair a fracture he suffered close to his left wrist in training yesterday.
It is a recurrence of the injury he sustained following a challenge from Tottenham striker Jermain Defoe in November last year, and will sideline him for the opening weeks of the Barclays Premier League season and Scotland's European Championship qualifiers against Lithuania and Liechtenstein in September.
But while his latest injury will come as a blow to the Edinburgh-born player, it leaves Bruce with a headache as he continues work to re-shape his squad.
Gordon's number two Marton Fulop has made no secret of his desire to leave the club in the search for regular first-team football with one eye on his international career with Hungary.
That seemed a likely scenario this summer following Fulop's emergency loan spell at Manchester City at the end of last season, and the arrival of 21-year-old Simon Mignolet from Belgian side Sint-Truidense in recent weeks.
However, Bruce will now have to weigh up his options and decide whether Fulop, Mignolet or 22-year-old Trevor Carson can plug the gap, or if he will have to make an unplanned dip into the transfer market.
Assistant manager Eric Black said: "The manager is going to have to reflect over the next 48, 72 hours to see where we go on that.
"We have been very encouraged by the two younger goalkeepers and the work they have put in and the quality of their training, so that's something he will obviously seriously consider as well.
"It's a problem that's going to have to be looked at pretty closely.
"But you have got to try to protect them as well. Trevor has obviously had more experience in the Premier League than Simon has, and yet Simon has played a year and a half in the Belgian league.
"I'm not saying it's the best league in the world, but it's a professional league with a lot at stake for the teams who are playing in it.
"Whether the manager will decide that it's too early, that may well be the case, but he hasn't made a decision on it as yet."