The Austria international only joined the club 12 days ago but was thrown in from the start against Barclays Premier League big guns Tottenham.
"I thought Paul was tremendous during the time he was on the pitch," Di Matteo told the WBA website.
"It was a difficult task for him in his first game. He has only been with us for 12 days. But he gave everything in the minutes he was on the pitch and he will only get better the more games he gets under his belt.
"I knew before the game he didn't quite have 90 minutes in his legs yet.
"But I thought he made a big contribution to our performance today."