Postecoglou admits he's been asking Tel to play out of position as he continues his loan from Bayern Munich.
He said at the final whistle: "Yeah, again, we're asking some big jobs of him, playing on the left and then in the centre. He's constantly learning. A lot of our guys I know will develop into top footballers.
"They have to go through this process of learning and adapting and understanding the demands of the Premier League and the demands of this football club.
"We've asked a lot of Matty since he's come in. He's pretty much played in every game at some point. He's taken in the information and he understands the role a little bit better, especially out on the left. Again, important for us.
"These last few weeks we've obviously had Sonny out. We've needed him to fill that void and I think he's done that job well."