Aluko pulled up in the pre-match warm-up against Sunderland last weekend and was a last-minute withdrawal, with subsequent scans confirming his worst fears.
The 24-year-old, who is Hull's most inventive forward by a distance, has torn his left Achilles tendon and Bruce does not expect to see him in the pitch until February.
It is a depressingly familiar story after Achilles trouble ended Aluko's season in January last term.
At the moment there is no indication that it is a recurrence of the same injury but Bruce admits there may be an underlying weakness.and could hardly hide his disappointment at the development.
"We've had some bad news; it's been confirmed that Sone has torn his Achilles and that's put a dampener on everything for us," he said.
"It's tragically hard luck. He broke down in the warm-up last week and it's just been confirmed he's got a tear which will keep him out until at least February.
"We await the specialists who are looking at the best way forward for him.
"He's had a few problems on it before but we thought we were over the situation. To damage yourself in a warm-up is quite ridiculous - it's sod's law, it's a warm-up he's done dozens of times - but there must have been a weakness there.
"It's been a little bit of an ongoing issue with Sone so whether it's all related we're not quite sure. We have to be patient now and hope we can see him in February."
Aluko's return of one goal in eight appearances in the Premier League - albeit a winner at Newcastle - does little justice to his role in the Tigers set-up.
He provides the link between the centre-forward and the midfield and occupies opposition defenders with his movement.
Hull do not have a like-for-like replacement in the squad and Bruce now faces a challenge to make do without him for another extended period.
"Anybody who's watched Hull City over the last 18 months, especially the first six months Sone was here, will realise I wasn't talking lightly when I said he was the best player in the Championship," said Bruce.
"He will take some replacing but we need to find a way. Whether that means changing the system or changing the personnel we need to enable the the team to function as well as it would do with him.
"Let's be fair, we've been without Sone a lot since last Christmas. He's played a few games this year but I would think only 50 or 60 per cent. We'll have to adapt and get over the loss."
Bruce spoke at the start of the season about the importance of keeping his first-choice players fit, but has had little fortune in that regard.
Captain Robert Koren and James Chester were early arrivals on the treatment table, with the former still battling back from a hamstring injury, while top-scorer Robbie Brady (hernia) and first-choice keeper Allan McGregor (hip/thigh) are both likely to miss Saturday's trip to Southampton.
"One thing you need at a club like ours, which has just come up, is your biggest and best players to be fit and firing.
"But that's football and we have to deal with it.
"Thankfully we've managed to cope with anything that's been thrown at us so far and hopefully that will be the case again."