Brendan Rodgers has vowed that Celtic will address their Champions League struggles in the January transfer window by adding extra quality in key areas.
The Scottish champions crashed out of Europe after losing to Lazio in Rome meaning they have registered just one point in five group stage matches so far.
Celtic were far from outclassed by their Italian opponents, but they ultimately failed to create and take that killer chance in the final third and they were made to pay for it by veteran striker Ciro Immobile who struck twice late on.
Speaking at full-time, Rodgers explained: "It's the overall quality. We need to have our very best players available.
"What makes the difference is that bit of experience and genuine quality. That's something we can hopefully resolve over the next couple of windows.
"This group has gained more experience and shown they can compete in some games - but we need to add quality. That's the glaring thing that stands out.
"We kept the ball but we needed to progress the game that bit more.
"Second half, we were much better, progressing the game through the pitch and managing the game well and then we arrived on the ascendency.
"In the last 20 minutes, we looked like the team that could go on and get the result, but we gave away two poor goals.
"The first one, we're in a great position up the pitch and we lose possession and never recover our shape. Then they get a bit of luck with the deflection. That was a tough one to take.
"For the second goal, we obviously need to be stronger and better."
Celtic picked up their only point against Atletico Madrid at Celtic Park and they now welcome Feyenoord to Glasgow in the final match of the group stage.
Looking ahead to the fixture, Rodgers added: "We want to finish on a high. We want to win in front of our own supporters. Our support has been incredible, travelling all round Europe.
"They haven't seen us win and we'd love to give them that victory at home and finish off with a positive result."
