Di Matteo rues early goals
Europa League winner Atletico demolished their English Premier League opponents in the showcase match at the Stade Louis II, Monaco.
Colombia striker Radamel Falcao, reportedly a one-time target of Chelsea's, netted a first-half hat-trick on Friday, with Di Matteo's team showing none of the defensive fortitude which took them to UEFA Champions League glory last term.
"I think we had a very slow start and we conceded two goals in 20 minutes and after that our game was very difficult," Di Matteo said.
"They started very well. We conceded a bit too much space to Atletico Madrid, and a player like Falcao, you can't give him that space.
"We said it before that's he's one of the top strikers in European football and again he showed it tonight, with the second goal he scored - it was a very good strike."
Di Matteo arguably has just two recognised strikers in his first-team squad, although wide attacker Victor Moses has arrived from Wigan Athletic to join Fernando Torres and Daniel Sturridge.
The Chelsea manager insisted his strike-force does not require further reinforcement, prior to the transfer window slamming shut later the same day.
"We have two very good strikers in Fernando Torres and Daniel Sturridge and I am very happy with the squad that I have.
"We have a good core of players and we've signed some young, exciting players, we need a bit of time to integrate them, but I am happy with the way the squad is."
Atletico coach Diego Simeone hailed to form of Falcao, who has now netted six goals in his last two matches.
"I am lost for words, there aren't word to explain how well Falcao is playing," he said.
"Today was a big game and with more pressure than normal. He was more motivated, and in these situations he performs better. He has a greater motivation to succeed ... than is normal."