The former Brisbane Roar and Wellington Phoenix stopper was sent from the pitch in the 71st minute for bringing down Mariners new boy Patricio Perez but replays showed there was minimal or no contact on the Argentinean and that referee Matthew Breeze got the decision wrong.
Grant, who scored the Sky Blues' opener, spoke for the whole club when he said he wasn't happy with the decision to send off Reddy.
''I only really got to see it on the replay but it's fair to say that we're not really happy about it,'' Grant said. ''The feeling after that was so deflating. Nobody wants to get a man sent off, especially a keeper, but I thought we hung in well after they equalised.
''We did a lot of defending but we also nearly caught them on the break a couple of times. Considering we were a man down, I thought we did pretty well."
Sydney are likely to appeal the red card and are confident that Reddy will have his mandatory one-game ban rescinded.