The Brazilian starlet, making his first start of the season for the Blues, fired the west Londoners into a 2-0 lead with a superb quick-fire brace after half an hour.
His fiercely-struck effort beat Gianluigi Buffon to put the home side ahead after 31 minutes, before his brilliant turn and sumptuous curled effort doubled their lead two minutes later – but the Blues were pegged back and held to a 2-2 draw by the Italian champions.
Di Matteo opted to deploy Oscar despite the 21-year-old having only made three substitute appearances in the league this term – but the Chelsea boss insists the midfielder is ready to push for a regular spot in his team, hailing him as a “big talent”.
“It was a great debut for Oscar,” said Di Matteo. “It was the right moment for him to start the game, we needed a bit of time to work with him and he was perfect tonight with the tactical information we gave him.
“The second goal was a wonderful goal and it is great to see we have a player like that in our ranks.
“He is a big talent and he has a bit of everything. We shouldn’t forget he is still a young man but he is quite established and he broke through to the Brazil team and that is quite difficult.”