The All Australian defender suffered the injury in the first half of Friday night's 17-point AFL loss to Richmond, but played out the game.
He is set to have surgery on Monday with the Saints confirming on Saturday that Dempster would miss three to four weeks.
Watters revealed the injury post-match and called Dempster's effort courageous, adding the backman was among many Saints whose effort could not be faulted.
He said the Saints medical staff had the final call on whether Dempster returned to the match after having to leave the field with the injury.
"He broke a bone in his wrist and he still was cleared, obviously," Watters said.
"We wouldn't put a player back out there if he wasn't cleared from our doc.
"It was an effort I admire and I thought there were a number of those from our players.
"There are minor fractures and severe fractures.
"It was taped and he was OK to play.
"There was no way that we would have a player out there if there was any potential long-term ramifications.
"Again, we rely heavily on our doctor."
Meanwhile, Saints coach Scott Watters said doctors made the call in allowing Dempster to return to the field with the fracture against the Tigers.
Watters revealed the injury post-match and called Dempster's effort courageous, adding the backman was among many Saints whose effort could not be faulted.
He said the Saints medical staff had the final call on whether Dempster returned to the match after having to leave the field with the injury.
"He broke a bone in his wrist and he still was cleared, obviously," Watters said.
"We wouldn't put a player back out there if he wasn't cleared from our doc.
"It was an effort I admire and I thought there were a number of those from our players.
"There are minor fractures and severe fractures.
"It was taped and he was OK to play.
"There was no way that we would have a player out there if there was any potential long-term ramifications.
"Again, we rely heavily on our doctor."
