Barry Robson pointed to a "frustrating" double-header against Hamburg as the main reason why Celtic ultimately crashed out of the Europa League.
The Parkhead side beat Hapoel Tel Aviv 2-0 at Celtic Park on Wednesday night with Robson's second-half free-kick adding to Georgios Samaras' opener. However, the first win of the campaign was not enough to prevent their exit with one Group C fixture against Rapid Vienna remaining, as Hamburg and Hapoel look forward to the knockout stages.
And Robson believes the games against Hamburg, where Celtic lost the Parkhead fixture 1-0 before drawing 0-0 in Germany, were crucial to the Hoops' fate, saying: "We have now played well in the last three games in Europe and we could have won them all. We missed a couple of chances at home and away to Hamburg, and everybody knows the stature of that club."
He added: "They have the biggest wage bill (in our section) and get money thrown at them in the Bundesliga.
"However, we more than held our own against them and probably outplayed them over the two games - so that is frustrating."
Robson will turn his attention to the Clydesdale Bank Premier League clash with Aberdeen on Saturday, where the Hoops will try to retain their place at the top of the table.
The Scotland international, though, referred to recent criticism of the Parkhead players by saying: "We need to win the next game. This is Celtic Football Club and we need to win every game that we can.
"There is always pressure at Celtic, everyone is saying we are not playing well, we are not doing this and we are not doing that. But we did play well against St Mirren at the weekend and against Hapoel.
"The majority of players have played in the last 16 of the Champions League and have won titles. So we are still very good players and if we get a few more wins we will start to build momentum."
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