The Royals have lost their last three games in the Championship after slumping to a 4-1 defeat at QPR on Tuesday night.
Brendan Rodgers' side are now fourth from bottom of the table and Celtic centre-half O'Dea insists they must arrest their alarming slide.
He told the club's official website: "You can talk all day, I'm sick of talking about it - it's about time someone does something about it. It's not for the want of trying, but you've got to have more than that.
"We need to look at ourselves in the mirror, get back here on Thursday and it's down to the 11 players on the pitch and the rest of the squad to do something about it."