Despite an encouraging start to the game, Bolton were well beaten against a clinical Reading team at the Madejski Stadium.
And Spearing, who completed the full 90, stressed the importance of immediately putting the game behind them.
He said: “What could have gone wrong did go wrong. We, as players, have to stand up and take responsibility because we haven’t been good enough.
“I’d like to apologise to the fans.
“Not one of us were anywhere near our best.
“As a group of players, our mental strength has to improve. We’re in it all together and we’ve got to hang in there.
“We’ve now got to move on and get on with it. There’s nothing we can do about the game now.
“There are no positives to take from the game, it’s as simple as that. We have to put it behind us and look to really improve ahead of the FA Cup game against Cardiff.
“Right now, it’s very difficult to take, but we can’t feel sorry for ourselves.
“We’ll be straight back in training on Sunday trying to put things right.”