Summer signing Oscar had fired the Blues into a 2-0 lead with two superb goals in as many minutes just after the half-hour mark at Stamford Bridge.
But the Italian champions fought back and Arturo Vidal narrowed the holders’ advantage with a well-taken finish before the break.
Both sides were careless in possession at times but it was Chelsea who were made to pay late on, when John Obi Mikel’s sloppy pass allowed Claudio Marchisio to slot in Fabio Quagliarella, who poked his finish through Petr Cech’s legs to salvage a point in the 80th minute.
“We feel a little bit deflated,” said Di Matteo. “We were ahead and have come away with a draw, but now we move on to the next game.
“We found ourselves in a great position to win the game. We knew we were playing a quality side. I think we probably made couple of mistakes on their goals, but they had good movement and quality for those strikes.”
Despite the disappointing start to his side’s title defence, Di Matteo was full of praise for Oscar after the 21-year-old Brazilian starlet announced himself to the Stamford Bridge faithful in stunning fashion with his quick-fire brace.
“It’s terrific for Oscar,” he contined. “We were waiting for the right game to put him in the team. His second goal was fantastic.”
And midfielder Mikel admitted his disappointment at Chelsea’s inability to build on a positive start to the game.
He said: “I think we started the game well. We scored two goals, then had more possession and had the game under control. The second goal was so cheap to give away.”