Celtic will open their Europa League campaign with a tough trip to Seville where they will take on Real Betis in their opening group game.
The Spaniards are the favourites to win the game and Celtic are without a number of key players who could have made a difference in Spain.
Celtic are without their captain Callum McGregor, who picked up a knock at the weekend, and new boys Liel Abada and Kyogo Furuhashi are also unavailable for the game.
Bartley conceded that Celtic would have loved to have the trio in their squad, but feels Ange Postecoglou has a strong group to work with.
He pointed out that Albian Ajeti grabbed his chance last weekend and feels in Spain it is an opportunity for some of the squad players to prove themselves.
Bartley said on the Go Radio Football Show: “They could have done with those players for sure but I think Ange has started to build a strong squad.
“We speak about opportunities all the time in football so the players who will come in for these have to this opportunity.
“Ajeti did at the weekend with a couple of goals.
“I am sure they are going to enjoy themselves and go in and put out a performance.”
Celtic did not make it out of the group stage of the Europa League last season in a massive disappointment for the club.
