Celtic lost 1-0 to Preston in a friendly as supporters returned to Parkhead for the first time since March 2020.
About 2,000 fans were allowed in for Ange Postecoglou's first game at Celtic Park and his final chance to hone his team ahead of their Champions League opener.
The Australian will be hoping for vast improvement for Tuesday's second-qualifying round first leg against Midtjylland after Ben Whiteman's second-half penalty consigned Celtic to defeat.
David Turnbull threatened a couple of times in the first half for Celtic but Preston looked the more likely team to make the breakthrough.
Vasilis Barkas was back in goal for the first half after suffering a finger injury in midweek and the Greece international made early stops from former Celt Scott Sinclair and Brad Potts.
Kristoffer Ajer, who has been linked with a move to Brentford, remained absent along with James Forrest, who missed Celtic's training camp in Wales because of a self-isolation order.
Ismaila Soro, Karamoko Dembele and Mikey Johnston were all absent after going off with injuries against Bristol City on Wednesday.
New signing Liel Abada, the 19-year-old Israeli winger, came on for the final half hour along with Tom Rogic and Odsonne Edouard, who have both been affected by fitness issues so far in pre-season. Boli Bolingoli came on too.
Preston also made a number of substitutions and took the lead in the 64th minute when Whiteman beat Scott Bain from the spot after a foul by the goalkeeper.
Celtic rallied and Abada and Ewan Henderson forced saves, and Rogic came close with a curling effort, but it was a second game in a row without finding the net for Postecoglou's side.
Meanwhile, Kyogo Furuhashi netted a farewell goal for Vissel Kobe ahead of his move to Parkhead.
The Japan forward scored in a 1-1 draw with Cerezo Osaka 24 hours after Celtic agreed a transfer deal with Kobe.
