Brendan Rodgers has rued the defensive lapses that saw Celtic crash out of Champions League qualifying at the hands of AEK Athens.

After a 1-1 draw in Glasgow, AEK were 2-1 winners in Greece as they seized upon errors in the Celtic back-line to ensure progress to the play-off round.

Rodgers admitted that the early exit was a disappointment and that the fault lay in "basic" mistakes at the back.

"Of course I'm very, very disappointed," he said. "I felt that in general in the game we played very well but we conceded two soft goals.

"Add that to the goal we conceded in the first leg and we're really disappointed in that aspect.

"In terms of lots of our game I felt that we were the better football team over course of the two games and in the main there wasn't too many opportunities against us but you can't concede that easily. And unfortunately it's cost us"

The Celtic boss said that the problem wasn't confined to the two-legged tie, highlighting goals conceded in previous rounds and in the opening two Premiership matches.

"There's been elements I've seen over the early parts of the season," he said. "We conceded against Livingston with a soft goal, against Alashkert with a soft goal, at Hearts we've given away a goal and over these two legs.

"We're not getting opened up and having fantastic goals scored against us. It's concentration and basic defending. So it's hard to get your head around but we have to go away and work with the players we have and try and improve and make them better.

"I always say you shouldn't have to lose to learn, but when you do lose you have to learn.

"That's our message and we get back on to the training field on Thursday and try to improve."

The manager reiterated earlier comments that Dedryck Boyata was fit to play but did not travel, and said that the defender "would have helped" if available.

Celtic will now face Spartaks Jurmala or Suduva Marijampole in the Europa League play-off and Rodgers said his team would be working hard to deliver European football for the months to come.

"Europa League is still a prestigious competition," he said. "Of course, the two seasons I've been here we've qualified for the Champions League.

"It's been a step too far for us this season so we first of all have to get through that final play-off game and ensure that we have European football.

"At this moment in time, it's just the disappointment from the game and obviously the way that we went out which is the only thing in my thinking."

Celtic defender Mikael Lustig echoed Rodgers' disappointment and said the players now need to show the right response.

"It's really hard to take but you need to bounce back," he said. "That's what makes a really good team if you manage to bounce back when you lost two games in a row.

"It's just get back on the horse and try to do better next time."