Atletico thrashed Chelsea 4-1 in last nightâ€™s European Super Cup.
Di Matteo said: "We had a slow start and conceded two in 20 minutes, so after that it was very difficult. They started very well, we conceded too much space and you can't allow a player like Falcao too much space.
"We were never in the game, they scored the first goal after six minutes and within 20 we found ourselves 2-0 down. We never got into the game and that's the most disappointing aspect. We had some possession in the first half but we lacked penetration. They retreated after the goals into a low block and made it difficult for us to find space.
"We gave too much space away, we've looked more solid so far this season, it's our game to be hard to beat but tonight that certainly wasn't the case."