The red card is the fifth of Cattermole’s Sunderland career and will see him miss three crucial Premier League games against Wigan, Manchester City and Newcastle.
"I feel sorry for [Cattermole] because he's been brilliant all season," Gardner told The Sunderland Echo.
"His attitude in training and on the pitch is spot on. He's a true leader and I just feel sorry for him.
"He's the last person in the world who wants to get sent off. He was rock-bottom in the dressing room afterwards and everyone was trying to pick him up."
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"Hopefully we will get him back in the team," he continued. "From where I was standing at right-back, it didn't look too bad. But I could be wrong. He was the other side of the pitch.
"We have got to get behind him and lift him up."