The Huddersfield boss admitted his side's 2-1 defeat at Exeter served as a wake-up call with the League One play-offs around the corner.
Lee Clark: "That was a smack across the chops. In all honesty it was a bit of a wake-up call for my lads.
"It just shows that when you are not 100 per cent there is a good chance that you might not get the result that you want.
"So we are going to be right at it in the first leg of the play-offs. We have got three cup finals and cup finals require passing, desire and commitment.
"There wasn't enough individual performances (against Exeter). I don't want to be too harsh on the players because it is a magnificent achievement to get into the play-offs.
"It is going to be a tough match against Millwall. But if we are going to get promotion then we are going to have to beat the best teams."