Celtic manager Ange Postecoglou stressed any new signings would complement and not replace his players as he hailed the "unbelievable" Anthony Ralston.

Ralston has been a revelation this season and enhanced his burgeoning reputation with another impressive performance in Celtic's 2-0 Europa League play-off first-leg win over AZ Alkmaar on Wednesday night.

The 22-year-old put in several excellent clearances and created some good chances, notably a late opportunity which led to Odsonne Edouard forcing a double save.

The former Australia head coach added: "I'm not bringing in people to replace people, I'm bringing in people to support the ones we have got here.

"It doesn't matter who the player is, it's inconceivable that they can play every game. Cal (Callum McGregor) probably thinks he can, and he probably could, but we have just got to be really careful.

"I am looking for players that are going to complement the ones we have got so we can build a strong squad, which we are going to need if we want to be successful. Especially playing the football we do.

"I have said right-back is a priority position because Anthony is the only one we have got. He is doing unbelievably well but he needs support."