The Newcastle United striker was forced off during last weekend’s 3-2 win over Southampton with a hamstring injury.
Wilson, the club’s leading Premier League scorer with 10 goals, is now facing up to two months on the sidelines.
“Unfortunately, Callum is a tear to his hamstring, and that could be six to eight weeks,” said Bruce. "It was a really, really fantastic victory for us, but the aftermath of it, losing three players, is a bitter pill to swallow.
"We hoped it was a grade one (tear), something like two to three weeks. Unfortunately, it’s worse than that. We’ll have to be without him for the best part of six, eight weeks. We’ll not put a timescale on it, of course, but it’s a bad tear on his hamstring. It’s devastating news for all of us.”
Fabian Schar, also injured against Southampton, has had surgery on his knee, while Javier Manquillo has damaged ankle ligaments.
Asked if Schar's season was over, Bruce said: “Hopefully not. It’s not going to be far off. He’s had an operation on his ligaments in his knee. Knowing the way Fab is, then he’ll everything he possibly can to get himself fit, because of the Euros as well, of course.
"He’s had the operation. It’s eight weeks, maybe. Manquillo did his ankle ligaments as well.”
Newcastle are 16th in the Premier League table. The club, which has won two of its last three games, is 10 points above the relegation zone.