Derry manager John Brennan has blasted his team's display despite beating Fermanagh 1-18 to 1-10 in Sunday's Ulster SFC clash at Celtic Park.
The Oak Leafers scored just six points in the second half after an impressive opening 35 minutes.
"I was happy at half-time but that was just rubbish football in the second half, " said Brennan.
"It was shabby, we let the supporters down and to say I'm disappointed is an understatement."
He added: "We didn't perform for 70 minutes - I want my team to play for 70 minutes.
"When you see good players making elementary mistakes, it is not good enough for the fans.
"We took some excellent scores in the first half although we had eight wides and some of the options we took were wrong."
Erne boss John O'Neill, who like Brennan was taking charge in the championship for the first time, admitted his young team has much to learn.
"We probably should have been three points up before they scored and we also had a penalty shout," said O'Neill.
"However, the occasion got to us in the first half and we know we can better football than that.
"We picked up a bit in the second half but still showed some naivety.
"It is a learning curve for the guys and it's back to work now for the next game."