The Black Cats fell behind to a Raheem Sterling goal before Luis Suarez added a double to seal the win for the Merseyside outfit.
Martin O'Neill's side have played four games in the last 12 days, but Colback refused to blame the busy schedule for the defeat.
“It would be just an excuse to say it was Christmas catching up on us,” he told The Chronicle. “It is the same for everyone with the amount of games.
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“When you have a small squad, it is tough, but it is part and parcel of football.
“We gave them two goals and then it was an uphill battle. It was a difficult night for us but made harder by our own slackness.
“The three goals we gave away could have been easily prevented. If you give them an early boost like that with two early goals then they are going to pass the ball around for fun and it is going to be hard for you.”
Despite the harsh scoreline, Colback said there were still a few positives to take from Sunderland’s performance on Wednesday night.
“Apart from their goals, we had the two best chances of the game," he added.
“We needed to come out second half and keep it tight and nick one, but it never happened. We conceded another and it was difficult then."