There is nothing riding on Celtic’s home meeting with Real Betis on Thursday night as they are already guaranteed to finish third in their group, and enter the Europa Conference League.
Postecoglou could shake up his starting eleven for the meeting with the Spaniards – and Hartson thinks that will give players an opportunity.
The Celtic legend urged those selected to stake their claim and make sure they show Postecoglou they are ready.
“This Thursday Celtic v Real Betis.. yes call it a dead rubber but always an opportunity for who comes in to put a marker down”, Hartson wrote on Twitter.
“A chance, an opportunity to shine to show Ange you’re ready.”
Postecoglou will want to see his side keep their winning momentum going with the visit of Real Betis.
The Spaniards are also in fine form and have won their last five games on the bounce, including victory at the Camp Nou against Barcelona.