McAtee curled in a winner for Sheffield United on the day at Bramall Lane.
Frank later said: "It was a difficult game. Fair play to Sheffield United. They did well in a game that was even and tight.
"I felt there would be a magic moment that would decide the game and that came from Sheffield United and McAtee. I can't complain about the effort from my players.
"This is the Premier League. You can quickly run into a patch of games and you can lose four in five. Unfortunately it has happened right now. We have to keep going. Injuries don't help any team.
"I think we have a little bit too many."