Brendan Rodgers said his Celtic side have an “awful lot of work to do” after their European campaign was ended by a limp 3-0 defeat at Zenit in the Europa League last-32.
The Bhoys reached the knockout stages of a European competition for the first time in three years but have not won a match at any level beyond the group stage since 2004.
They took a 1-0 lead to St Petersburg on the back of a dominating performance at Parkhead last week, but were deservedly knocked out following a timid showing, where they failed to register a shot on target until the 67th minute.
“There’s still an awful lot of work for us to do,” Rodgers said. “If I take a step back, there has been a lot of positives for us in European football this year over both competitions.
“Last week was an outstanding performance and we came into this game with a great opportunity to come through, but if you don’t start with that aggressive mentality, then it’s really difficult for you.
“We now have to go away and finish the domestic campaign as well as we possibly can and try to create another piece of history on that front. We then need to try and be better in Europe like we were this year and take another step forward.”
Celtic’s lack of belief was their undoing against Roberto Mancini’s Zenit, and left them struggling to create anything likely to test home goalkeeper Andrey Lunyov for long periods.
That was what disappointed Rodgers the most, considering their confident performance at Parkhead only a week before, having turned an aggregate advantage into an uphill struggle in the space of 27 first-half minutes.
He said: “Across the two games, we were much the better in the first game and in this game, if we played with a bit more courage and belief, we could have maybe got a result.
“You talk about defending forward and we didn’t do that well enough, and we conceded poor goals from that.
“At 2-0, we still have an opportunity in the game. We said at half-time everything was too sideways and backwards and that’s about bravery and courage to play.
“You saw the contrast from last week. In the second half we started off ok but then you concede possession too cheaply and they work ball around for a cross, and then they get the third goal. We shouldn’t be conceding that type of goal.”