Celtic were given a pre-season warning as Dukla Prague eased their way to a 5-3 win over the hoops at St Mirren Park.
With four victories behind them already the Czech side were a cut above what Celtic had to offer as Ronny Deila’s side prepare for Champions League qualifiers.
Celtic had no answer to the hat-trick from Marek Hanousek with the hoops goals coming from Leigh Griffiths, Gary Mackay-Steven and Virgil van Dijk.
With ten days to go before the Champions League qualifier against Stjarnan Ronny Deila brought back his big hitters with Scott Brown, Craig Gordon, Griffiths and Stefan Johansen in the starting XI.
Charlie Mulgrew partnered Dedryck Boyata in the centre of defence with a view to the Stjarnan tie which van Dijk will miss through suspension.
Dukla arrived in Paisley after winning four pre-season matches and were a clear step up in class from Den Bosch who seemed happy enough to accept a 2-0 defeat on Wednesday.
The Czech side had already tested the Celtic defence a couple of times before Hanousek struck the opening goal in the 13th minute with a low 20 yard drive beyond Gordon.
Just before the hour mark Celtic were back on level terms when Griffiths scored from the penalty spot after Lustig was pushed over in the box.
Dukla were unfazed by losing that goal and continued to push forward at every opportunity forcing Scott Brown and Tom Rogic into some frantic back-tracking to protect the hoops defence.
In the 36th minute Dukla restored their lead with Hanousek again on target with the midfielder denied his hat-trick by the crossbar three minutes later.
Two minutes from the half-time break Celtic were back on level terms when Mackay-Steven got behind the Dukla defence to get on the end of a Johansen pass and push the ball behind the advancing Dukla keeper.
At the interval Deila made four changes with Emilio Izaguirre the only defender to remain in the side with Leo Fasan, Darnell Fisher, Virgil van Dijk and Efe Ambrose replacing Gordon, Lustig, Rogic and Boyata. Mulgrew stepped into midfield to replace Rogic.
The new look defence had barely had time to find their feet when Hanousek completed his hat-trick in the 49th minute from the penalty spot after a referee John Beaton blew for a foul by Mulgrew.
There was a worrying flatness about the Celtic performance which was hardly surprising since the bulk of the side had been involved in Euro 2016 qualifiers just three weeks ago.
Dukla went further ahead in the 59th minute when Jakub Mares sent a glancing header beyond Fasan following a cross from the left.
Deila introduced five more substitutes but the changes failed to change the pattern of play with Dukla looking sharper in every area.
With seven minutes left to play van Dijk headed Celtic’s third goal of the day but two minutes later Tomas Prikryl scored Dukla’s fifth goal with a low angled drive around Fasan.
Celtic return to Paisley next Friday to face Real Sociedad with Deila certain to demand improvements before his venture into European action.
CELTIC Gordon; Lustig, Boyata, Mulgrew, Izaguirre; Brown, Rogic; Forrest, Johansen, Mackay-Steven; Griffiths
SUBS: Fasan, Fisher, Ambrose, O’Connell, van Dijk, Tierney, Henderson, Lindsay, Nesbitt, Donnelly, Stokes, Scepovic, Trialist, Thomson, Boerrigter, Hazard
