The Blues sit in 21st position in the standings after losing four of their last five matches, and Robinson has insisted that the club's plight hasn't been helped by the performances of some of the players acquired during the January transfer window.
The 35-year-old told reporters: "The big clubs send these players out for a reason and that's to get first-team football.
"For me, they've let the gaffer down, they've let us players down, some of them, and they'll just go back to their clubs and get on with it.
"That hurts the most because we're football players and we're brought up to love the game. Do these young kids love the game as much? I don't think so."
Birmingham host Leeds United on Saturday afternoon.