Bruce said that he knows "for a fact" that Boyd is not the type of player to do such a thing and believes that it is clear in the video evidence that it was an accidental spit.
"We have to deal with the loss of him now," Bruce said in his pre-match press conference. "He'll be disappointed to hear that and it probably makes a bad week for him worse.
"Anybody who knows him will know for a fact that he would never, ever spit at anybody deliberately. No chance. It's not in his make-up. He's horrified at the charge, genuinely horrified. He's shouted at him and [saliva has] come out of his mouth. I'm 100% behind him."
The first game of Boyd's suspension will be Saturday's home clash with West Bromwich Albion.