Lee Johnson admitted Oldham's poor second-half performance led to their 1-0 defeat to Derby in the Capital One Cup.
Latics created early chances in the first-round tie as Adam Rooney and Jonson Clarke-Harris both fired off target from inside the penalty area.
But the Rams snatched the decisive goal after 20 minutes when Conor Sammon crossed from the left and Michael Jacobs drilled home from six yards.
"It was a decent game and both sides had their chances, but I'm disappointed with our second half," Johnson said.
"We were all about the first-half performance and I found out here that we don't have a Championship mentality.
"At times our football can be at that level, but we have a lot of young players and you can't coach experience.
"That means you have to work on partnerships and relationships and improve the bad bits, which is what we'll do.
"Our inexperience showed against a very good side. We fizzled out after half-time, but we certainly didn't disgrace ourselves.
"We want to play out from the back and we have the players to do it, although we won't try to be Barcelona because sometimes the best option is Row Z.
"We did well overall and, as a young team, we are only going to get better."