ADAM Smith believes Millwall must learn quickly from their mistakes against Barnsley ahead of Hull City's visit to The Den on Saturday.
Smith felt the Lions struggled to come to terms with the Tykes' five-man midfield as they slipped to a disappointing 2-0 defeat at Oakwell in midweek.
The high-flying Tigers utilise a similar system, lining up in a 3-5-2 formation, and Smith says Millwall cannot afford to make the same mistakes again.
"We struggled with Barnsley's midfield," Smith said. "Jim O'Brien was in the hole and I did not think we coped with that well enough - he kept getting the ball and turning.
"We were exposed defensively so maybe we could have done better there. The gaffer will work with us on the training pitch to stop that system before the Hull game.
"We knew ourselves as players that the performance in midweek wasn't good enough. We were all saying that in the changing room. The gaffer didn't really need to say anything.
"We were a bit too deep defensively and there was too much space between our back four and midfield. It was one of those tight games where whoever got the first goal had a big advantage."