Keath was sidelined during Gather Round after a head knock against Richmond in Round 4, but will re-join the Bulldogs to replace Bruce, who is sidelined indefinitely with a rib injury.
Bruce failed to play out the Bulldogs' loss to Port Adelaide after being part of a heavy collision, with the club subsequently revealing that the 30-year-old suffered significant rib and sternum damage.
Speaking to media on Thursday, senior coach Luke Beveridge confirmed that the Dogs would be forced into the change ahead of Friday's clash.
"He'll replace Josh," Beveridge said.
"It is unfortunate, Brucey was going really well. He'd made the adjustment; he'd had a good pre-season and been a terrific contributor in that back end. It is really bad luck, so he is going to be out for a while, Josh.
"Alex's form is tremendous. He played a cracking game the week before against Brisbane before he got injured. We welcome him back and hope he can play well for us."
Beveridge also confirmed that Bailey Smith will miss again with a calf injury, with the young Dog yet to return to full training this week.
"He's got an important session tomorrow," he said.
"He hasn't really done much yet with the calf injury, so we'll wait and see how he pulls through some training to see whether or not he is available for the following week. We can't give you much more than that unfortunately."