Brady is Hull's top scorer with four goals in all competitions, but his season has been disrupted by a hernia operation in October.
The 21-year-old is still being dogged by the problem and Bruce is concerned for the midfielder.
"Robbie still isn't right," said Bruce.
"It's something we're going to have to explore more deeply because it's grumbling along.
"He came on last weekend and was still complaining about it and it is a worry for us.
"We do need our big players to be playing and certainly Robbie can give us something going forward.
"It's a complex one. He had an operation on it and he's not really recovered from that.
"We now need to go down a different route, explore it and make sure he's right."
The absence of Brady is offset by the news that defender Alex Bruce is fit after recovering from the knock that forced him off in last Saturday's goalless draw with Stoke City.
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