"There's two ends of the pitch - we've played fantastic at one end, created chance after chance," said Wilson. "We've taken a couple and maybe should have been four up at half time.
"Second half - we've done the same again. We've come back and created chances but at the other end of the pitch - it's been quite poor in every department of defending.
"We've just not been able to compete with one ball that's come down the middle on three or four occasions and they've resulted in goals.
"The crosses that have come in the box have been too easy to come in. They've finished off with easy goals. They've had four chances maybe, and three of them have ended in the net.
"We must have had 12 or 14 chances, and I would suggest eight or nine of them are excellent chances.
"There's lots of aspects of the game that will get forgotten. But we'll look at the result and forget the good parts of the game. But that's what happens.
"There was lots of aspects, in the attacking play which was excellent. But the defensive side of it was poor - very, very poor - and that's something we have to address."
Devante Cole and Conor Hourihane scored in the space of four minutes to give Barnsley a lead that could have been extended before the break.
"He (Cole) was a big threat all night for us," said Wilson. "Him and Sam have done well at times. Devante, in particular, was excellent. Every time he got anywhere near the ball, they've ended up with a panic on.
"He could have had three or four goals but we can't rely on one person."
