Di Matteo: Champions League field stronger
The Londoners have also been drawn alongside Shakhtar Donetsk and Danish newcomers Nordsjaelland and Di Matteo is wary of all of his Group E opponents.
"We have three national champions in our group, from Italy, Ukraine and Denmark, so it will be difficult," the Italian told a news conference at Stamford Bridge on Tuesday.
"It's not just them either - other teams who have joined the Champions League this season are very strong. It's very competitive and probably even stronger than last year."
Chelsea found it tough enough to win the competition last season, overturning a 3-1 first-leg deficit to oust Napoli in the round of 16, knocking out favourites Barcelona in the semi-finals and beating Bayern Munich at the German club's home ground in the final.
"When you are at a club like Chelsea there is always pressure to win trophies and bring more success," said Di Matteo.
"Everybody was pleased we brought the trophy home to Stamford Bridge for the first time but we have to look forward now, that's in the past," added the Italian who was promoted from caretaker to full-time manager in the close season after winning the Champions League and FA Cup in May.
Chelsea midfielder John Obi Mikel is certainly looking forward... to pitting his wits against veteran Andrea Pirlo.
The 33-year-old Juventus playmaker was one of the best performers at Euro 2012 in Ukraine and Poland and Mikel cannot wait to get a close-up glimpse of the gifted Italian international.
"Pirlo is a great player and has been in the game a long time," said the 25-year-old Nigerian. "Every day I go in to training I like learning, even from the younger players, and I am always open to new things.
"Playing against a legend like Pirlo is going to be great but I also want to win so it is going to be a battle. He wants to win and I want to win but I respect him as a player and hopefully I can learn from him tomorrow."