John Hartson insists Celtic are now "playing for third" in their Champions League group after the defeat to Lazio.
The Hoops lost 2-1 to the Italian side after a late winner from Pedro and the former Parkhead striker feels it will be a step too far for them now to progress in Europe's premier competition.
Hartson reckons the Europa League is Celtic's best chance of still being in Europe after Christmas.
He told The Go Radio Football Show: "Realistically we are playing for third place now. You can't afford to lose your first two games and third place on the back of losing the first two games would be a huge success now.
"It would be bouncing back. So, tough games, I think Atletico Madrid are the best team in the group. I think the home game will be similar to the Lazio game.
"I think we'll have chances, I think we'll have the ball, the crowd will push us on. We have got to try and get something, preferably a win.
"I thought we did everything the other night, I am not too sure in Feyenoord. Stop conceding set-pieces, first and foremost, defend strongly.
"The other night we conceded another set-piece having gone in front. I know we don't have a lot of height in the team.
"Luis Alberto, brilliant delivery into the box, it's the second ball. It's not initially the first one but reacting to the second one so we have to defend properly, that goes without saying.
"I think sometimes when you go 1-0 up, you have to go for the jugular, you've got to try and get two. A lot easier said than done and it's not a magic wand.
"Almost all the big teams in Europe that we play can monster Celtic's budget>"
