Port Vale manager Micky Adams has admitted he started with the wrong team in their 1-0 defeat at Colchester.
Adams switched to to an unfamiliar 3-5-2 formation after the midweek loss to Walsall, but still saw his side beaten.
"We started off with a system that didn't work and I'll put my hand up to that, I picked the wrong side," Adams told BBC Radio Stoke.
"But I'm really disappointed with the performance. I think that's as poor as I've seen us for a while."
Gavin Massey's goal separated the two sides at the Weston Homes Community Stadium, leaving newly-promoted Vale still seeking their first win of the League One campaign.
And Adams explained the reasoning behind his decision to change from the 4-4-2 formation they used against the Saddlers.
"When we saw Colchester down at Gillingham, they had three centre-forwards that played really close together, so I thought I would stifle that a little bit," he said.
"We were playing offsides when they've got time on the ball. We're not the sort of side that tries to catch people offside - we normally stay with runners.
"I thought the level of enthusiasm for the game wasn't there for some reason."
Despite their defeat, Adams, whose side finished third in League Two last season, backed his players to recover.
"I don't want to go overboard about our performance. We'll study it and analyse it and get back on the training ground," he said.
"We've got an honest group of players and if I say they lacked enthusiasm, I'm sure they'll take it in and respond next week."