Ronny Deila's men lost 5-3 against the Czech side during a pre-season friendly.
There is, of course, no need to panic after a friendly defeat. That's what pre-seasons are for: testing players, getting fitness up and trying new things you wouldn't necessarily when the result counted towards a league or cup run.
And that's why Celtic's 5-3 loss to Dukla Prague on Saturday afternoon doesn't mean all that much. As boss Ronny Deila promised fans after the game, the same mistakes that happened against Prague won't happen when his Bhoys squad are fully fit and match sharp.
That said, both Deila and many of the Celtic faithful openly admitted at the end of the game there are things that need to be worked on. Particularly as the Hoops face Champions League qualifiers not too far in the future.
As such, several Celtic players were the subject of scrutiny from fans on Twitter during and after the 5-3 defeat. And none more so than 29-year-old Charlie Mulgrew, who was accused of being too slow to keep up, with some Celtic supporters even calling for him to be sold before the competitive season begins.
Harsh criticism? Plenty on social media felt not...
He's Charlie Mulgrew, he's slower than me or you. 3-2 Dukla from the spot.— yahmpy (@yahmpy) July 4, 2015
Someone please put Charlie mulgrew in the bin— Fanny Dillion (@hanzbooby) July 4, 2015
Celtic need to get rid of ambrose, mulgrew and stokes. Simply not good enough— Ray (@Rama1978) July 4, 2015