Celtic lost on penalties to Leicester City on Saturday afternoon.
Celtic kicked off their International Champions Cup campaign with a 1-1 draw against Premier League champions Leicester City, before losing on penalties.
The Bhoys - playing in front of their home crowd - went behind when Riyad Mahrez cut inside and curled a superb left-footed strike into the top corner of the net.
However, Celtic did respond, and young defender Eoghan O'Connell struck to equalise for Brendan Rodgers' side, sending the game to penalties.
Just one spot kick was missed, as James Forrest saw his effort saved, handing Daniel Amartey the chance to give Leicester the win in Glasgow - and he duly obliged.
The end result will have left manager Rodgers disappointed, but his side went toe-to-toe with the Premier League champions, prompting praise from John Hartson on Twitter.
Welshman Hartson, a former Celtic player, took to social media to state that he felt Celtic were 'excellent' against Leicester, especially in the second half of the game.
Eoghan O'Connell celebrates with team mates after scoring the first goal for Celtic
However, he did add that the key game is Wednesday's trip to take on Astana in Kazakhstan, as qualification for the Champions League is far more important than a pre-season game.
Thought Celtic were excellent today against a really good side. 2nd half especially. Big picture is Wednesday of course. #hoops— John Hartson (@JohnHartson10) July 23, 2016
Eoghan O'Connell scores for Celtic
After Celtic's trip to Kazakhstan, they will then head to Dublin to face Barcelona in the International Champions Cup, before facing Inter Milan in Limerick in August - six days after the league season begins.
Rodgers will be encouraged by what he saw against Leicester, but his players must now do it in competitive action - something Hartson was quick to point out even when praising Celtic for their display on Saturday.
What did you think of Celtic's performance against Leicester?