Terim's side made a horrendous start in their bid to reach Euro 2016 from Group A as Iceland embarrassed them in Reykjavik.
Jon Dadi Bodvarsson, Gylfi Sigurdsson and Kolbeinn Sigthorsson all scored for Iceland, while Turkey had Omer Toprak sent off for a second yellow card in the 59th minute.
Patience among Turkish football fans is not high after three successive failures to make major tournaments.
Terim – who said he was "very much disappointed" with the result, added: "I was worried before the game that the team was not totally ready.
"I congratulate Iceland, they played better than us and we deserved the loss. I hope that such a thing will not happen again.
"If we had not dropped down to 10 men, we might have brought the game to a draw.
"Only players who can cope with this level of football will continue with us. The national team is where you should perform 100 per cent."
