Nottingham Forest boss Colin Calderwood has warned his promoted side their "mistakes will get punished" at Championship level next season.Calderwood lead his Forest side to final-day promotion glory as they defied the odds to edge out Carlisle and Doncaster in the race for the second automatic spot.

And, despite his defence leaking just 32 goals last season - the fewest conceded in League One - the Scotsman believes they will have to become even meaner in order to cope with the added pressures of second tier football.

"It will certainly be more physical," he told the club's official website. "We've got to find out whether we can cope with playing at that different level - can we gain control of the ball as much as we did last season? We'll have to be tighter than we were last season.

"We made mistakes but they weren't punished, which led to us having an excellent defensive record.

"But those mistakes will get punished more severely next season. That's where the improvement has got to come."

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