Middlesbrough boss Gareth Southgate was unimpressed with his side's display in the hard-fought 1-0 victory against rock-bottom Derby County.
Tuncay 32nd-minute goal proved to the only difference between the two teams and the Rams almost grabbed a point in the closing stages strike when Robert Earnshaw wasted a good chance.
Southgate said: "We've seen it through today, and they weren't able to punish us - but we can't play like that.
"They should have scored, and we would have been sitting here frustrated again.
"We've got to be better than we were in the second half. We've got to be bolder and be willing to attack more. At the moment we tend to go into our shells, because of the importance of the points.
"Guts has got them over the line, but we have got to be mentally tougher and braver in the way we finish games.
"I think they are learning as a team and scrapping as a team and grafting for each other."