Postecoglou’s two usual academy players Mikey Moore and Will Lankshear were joined by two talented defenders in Dorrington and Cassanova as well as 18-year-old winger Ajayi as they look to break into the first team.
Dorrington has recently returned after a long recovery from hamstring surgery and is said to be a mix of Cristian Romero's strength and comfort on the ball as well as Micky van de Ven's confidence to run forward with the ball and make chances.
Cassanova has played a vital role in the U21 side in recent years due to his versatility as he can play at centre back as well as at fullback.
Ajayi is a quick winger, his pace and agility are unmatched in the academy and Postecoglou will be eyeing him up as he looks to rotate his side before this weekend's clash against Brighton & Hove Albion.
All three of the players have been added to the Europa League B list for youngsters as they look to make the substitute bench and possibly earn some valuable minutes in the Europa League.