The Latics conceded an injury-time equaliser to Blackburn at the DW Stadium on Saturday and remain at the foot of the Premier League table with six points from 12 matches.
"I thought we were a different class on Saturday so it is frustrating," said the 21-year-old on the club's official website. "There are a lot of games to go and although we are down we have to pick ourselves up to go to Sunderland.
"We have a massive away game; to be honest every game from now to the end of the season is massive.
"We will go to Sunderland and give it our best shot. They will be fighting to get higher up the league as well."
Against Blackburn Latics boss Roberto Martinez made five changes and McCarthy has defended the Spaniard.
"It is a squad game and the gaffer makes changes and you have to take it on the chin and hopefully, when you get a chance, try to stay in the team," he said.