Bradley Johnson had put Norwich ahead at Carrow Road just after half-time as the Canaries looked to pull further clear of the Barclays Premier League relegation zone, but Chris Hughton's side were pegged back courtesy of a Walters penalty 17 minutes from time.
But Walters' celebrations were short-lived as he was shown a straight red card less than five minutes later after catching Alex Tettey with a high challenge.
"I've looked at the incident and there is contact and Jon has accepted that he caught him," he said.
"But both players had their feet high and I think the punishment was too harsh for the crime. Both players just intended to win the ball and Jon just caught him with his follow through.
"It was the first sending off of Jon's senior career so he is obviously very disappointed and he now misses three games.
"As for the penalty, Guidetti was impeded and Jon as always, took responsibility and dispatched it with aplomb. At that stage I thought we would go on and win the game but then the sending off changed everything."
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