The BBC pundit stood firm on Twitter, despite criticism aimed at the Celtic defender.
Indeed, Hartson feels Efe Ambrose should start for the Hoops in Sweden - and that's despite an impressive Saido Janko performance on Saturday afternoon.
Janko performed well during Saturday's 3-1 win at Dundee United and fans have been raving about the full-back as a result.
So, when Hartson tipped Ambrose, Celtic fans responded asking about the younger alternative.
But the BBC pundit stood firm and hit back at criticism aimed at Ambrose, with the tweet he was replying to later being deleted.
Tell Deila if I tell him I'll be hammered!! https://t.co/jjsjE7ToHl— John Hartson (@JohnHartson10) August 22, 2015
The choices facing boss Ronny Deila, of course, could define Celtic's season. Whether it's Ambrose or Janko, a midfield conundrum or who to play out wide, the Bhoys boss needs to be at his sharpest both motivationally and tactically.
Not only are Celtic one game away from the Champions League group stages, they are potentially a 0-0 draw away from them should they keep a clean sheet. But selection dilemmas after Saturday's win over Dundee United are welcome ones to have. The Bhoys certainly showed some strength in depth.