Reds Manager Danny Wilson has called on his side to cut out the 'sloppy goals' as he prepares his squad for Crewe this Saturday.
The Alex left Oakwell on Tuesday night with a 2-0 victory in the Capital One Cup First Round, and the Reds head to Gresty Road on Saturday in the league.
Speaking to Barnsley Player this morning, Wilson said, "We have to be tougher and stronger defensively.
"We’re not always going to be able to attack and we’re not always going to have the ball.
"We’ve got to be as determined as we were the other night. I felt we played some good stuff. I don’t think we played badly whatsoever. We conceded two goals that were avoidable.
"It’s out-of-possession which makes you a good team as well - that discipline, that strength and that determination to defend, where you’re a striker or a defender."
Nine of Barnsley's 20 shots were on target, but the Reds failed to beat Crewe 'keeper Ben Garratt.
"We have to stick our chances away," continued Wilson. "We had a hell of a lot of chances in the game that we should have come away with something, quite honestly. Those are the two key areas - both boxes. What did please me was the fact that we did create things.
"The amount of times we opened them up and created opportunities suggest that we’re getting there.
"If two or three of those chances had gone in in the last two games, it’s a different scenario.
"When we hit the back of the net, we’ll see a different team and we’ll grow with confidence. Then all of a sudden you’ll think they’ve settled in alright."
The Barnsley boss is still waiting on defender Joe Dudgeon, 'keeper Ross Turnbull and striker Kane Hemmings to see whether they'll feature this weekend.
"They’re getting closer to matchday playing," he added. "What we have to do is be patient with them. The one thing we don’t want to have is for them to be out for any longer period of time. We’ll look at Saturday and there might be one or two changes but we’ll be able to determine that when we’re closer to the game.
"We have to learn from what we’ve just had in the last 72 hours or so. Going back to what I said before, we have to make sure we don’t concede the goals we have – they’re too sloppy.
"But one thing that has particularly pleased me is that one or two individual performances are getting stronger and better. As a unit, we have to make sure we tie down certain things at certain times in games."