The highly-rated 20-year-old is currently in London as he prepares to compete in the Olympics with Brazil. Although the Blues have already secured midfielders Eden Hazard and Marko Marin, speculation has persisted recently that they are determined to add Oscar to their ranks.
Di Matteo told the club's official website: "I can tell you that he's not a Chelsea player so it's difficult for me to talk about a player that doesn't belong to us."
He added: "I know there has been speculation we are interested in this player and in due course if there is anything to announce we will do.
"All I would say is that he is a very young talented midfield player."
For his part, Oscar reportedly told journalists in Rio before travelling to England "I'm staying" when asked about the possibility of a move to Stamford Bridge.
Meanwhile, Hazard's younger brother Thorgan is also on the Blues' radar, according to Lens sporting director Antoine Sibierski.
The 19-year-old winger has played only 11 times for the French Ligue 2 club and has just a year remaining on his contract.
"I've since learned that Chelsea are interested in his possible arrival. I can understand why a player would want to leave Ligue 2 to go to Chelsea. We're in discussions," Sibierski told La Voix du Nord newspaper.
"Now, like in every transfer with a year left on his contract, it must be paid for. There are also compensation fees for training him."