Celtic chairman John Reid has reiterated the importance of European football after interim financial results for the final six months of last year showed a decrease in turnover of 21.4% to £28.4 million while bank debt almost trebled to £9.1 million.
Celtic suffered a severe financial blow by being knocked out of the Champions League and then Europa League at the first hurdle this season.
And although profit before tax rose to £7.1 million from £1.3 million, that was largely down to the sale of Aiden McGeady to Spartak Moscow for £9.5 million, with the club warning the second part of the season would be "more challenging''.
It was also revealed that manager Neil Lennon has spent £9 million on players.
Reid revealed a reduction in European home games from five to two had been a key factor in revenue falling by almost £8 million to £28.4 million, with profit from trading down from £4.7 million to less than £1 million.
"In previous years, and again last summer, I stressed the importance to our club of financial stability and participation in Europe, and that commercial and football success cannot be separated,'' he told the club's official website.
"At this time last year we knew we were facing a very difficult season, and so it proved. In turn, that left a legacy of setback at the beginning of the current season, in dropping out of European competition entirely at an early stage.
"But while some of the economic and financial issues that we would face as a result could be predicted, we had little inkling of other events which will undoubtedly play a large part in shaping the future of football in Scotland.
"The cold wind of economic recession, combined with the effects of the eve colder Scottish winter and our early exit from Europe, are reflected in disappointing underlying trading results for the six months to 31 December, 2010.''
Celtic cut their operating expenses by almost £4 million but Reid admitted that "player trading'' had become increasingly important to the balance sheet.
"We continually seek to improve and refresh the first team squad through development of our own young players, and the introduction of new players from elsewhere,'' the chairman said. "This also means moving on players who we consider are underperforming and selling others who are important to us, if the timing and price are right and/or the individual concerned himself wishes to leave the club.
"McGeady, McManus, Boruc, Fortune, Sheridan and Mizuno left us during this period, and in thanking them for their service we wish them well for the future.
"The contribution generated from player trading more than offset the outcome on our other trading activities and enable us to report an overall profit before taxation in the period of £7.06 million. However, in common with previous years, the second half is expected to be more challenging in terms of financial performance.''