Di Matteo masterminded a second straight win in Europe, this one achieved despite the Italian resting six of his increasingly-tired players. After the 1-0 success against what was a toothless Benfica side, the Chelsea caretaker manager claimed his side still had a mountain to climb.
He said: "I think we've put ourselves in a good position, but it's not a result you can rely upon for the home game. It's one goal."
He added: "You look at he results Benfica have achieved in this Champions League... you're not going to sleep very calmly looking at that."
Only twice has a side come back from losing the first leg at home, although Chelsea became only the fourth team to triumph after suffering a defeat by two or more goals in the away leg when they beat Napoli three weeks ago.
Di Matteo added: "We are pleased that we're in a different position going into the second leg. We had a mountain to climb against Napoli. We still have a mountain, but it may be a little bit smaller because we've achieved a good result here."
Di Matteo admitted he took a risk with his team selection, which saw him leave out Napoli heroes Frank Lampard, Didier Drogba and Michael Essien and hand rare starts to Paulo Ferreira, John Obi Mikel and matchwinner Salomon Kalou.
The Italian said: "I'm involving everybody that is in the squad, rotating. We'll need everybody until the end of the season."
Benfica boss Jorge Jesus claimed Chelsea were lucky to win, saying: "We were superior in many things to Chelsea, but they were luckier in one moment. We had more opportunities. We didn't deserve to lose.
"We were the better side for long periods, had more shots on goal and Chelsea didn't see much sight of our goal. But what counts is the result."
Source: PA
Source: PA