Miller was shown a straight red card for shoving Claudio Pizarro in the face.
Keane said: "For the red card, there's no doubt that when you raise your hands you don't give the referee any choice.
"But it could have been avoided. There was a big issue made out of Liam's tackle on John Terry.
"John and Claudio Pizarro had a go at Liam. Obviously it was a foul but that was it, there was no nastiness to it.
"Now he'll miss the next three games. Maybe the referee could have stepped in five seconds earlier.
"But John and Pizarro's reaction disappointed me."