NEIL Harris has warned his players to up their performance levels in training to avoid making the types of errors that cost them two goals at Barnsley.
Sam Winnall punished some slack marking to head his side in front, before the striker set up Adam Hammill for the second after Millwall had lost possession in midfield.
The Lions had a number of chances to find an equaliser, the best of them in added time at the end of the game when Steve Morison hit the crossbar with a header and Lee Gregory's follow-up was cleared off the line, the fourth time Barnsley executed a last-ditch escape in the second half.
But it was the manner of the defending at the other end of the pitch that concerned Harris.
He explained: "We coach the players on the training pitch, we show them videos. But you can only coach them to a certain degree. The players have to take responsibility themselves.
"Unfortunately for us other players on the other teams tend to move on the football pitch, so we can't physically put the players in the positions that we want.
"The players were fantastic at Southend, we were solid and we scored four goals. We were buoyant all week and really positive. I think it's just a realisation about where we are.
"We need to stop the errors. If you're sloppy during the week in training then you're going to be sloppy on matchdays.
"We made some bad decisions. Some players wanted to play their own style of football rather than play to the strengths of the team."
Harris did, however, draw some positives from the performance of David Forde at Oakwell.
Forde started his first league game since August in the 1-0 defeat to Walsall on Boxing Day after Jordan Archer's sending-off against Gillingham the previous Saturday.
He held onto the number jersey after Archer had served his ban, keeping a clean sheet against Southend before pulling off a couple of excellent saves in the second half against Barnsley.
"I thought Forde was outstanding," Harris said. "That's his third game in there. Obviously Jordan was unfortunate with the red card but Fordey's taken his opportunity to come back in and he's performed outstandingly well.
"He gives us real leadership. It's strange to be talking about the goalkeeper when you feel you should have got plenty out of the game. But I thought he made some very good saves and was really assured."