Rafael Benítez feels he has not had long enough with his players at Internazionale after losing his first competitive match last night, when the European champions were beaten 2-0 by Atlético Madrid in the European Super Cup final in Monaco.

Goals from José Antonio Reyes after 62 minutes and a simple tap-in from Sergio Aguëro seven minutes from time gave the Europa League holders a surprise win over the Italians – who won the treble last season – at the Stade Louis II.

Afterwards Benítez, who replaced José Mourinho in the summer, admitted that Inter were not at the level they need to be and cited a lack of preparation time with some of his World Cup players.

"Some things we will need to do in the same way as we did before and change the way we do some other things," said the former Liverpool manager. "It's clear we will need some time, but how long you never know. We have not had much time since the World Cup with the players. We were not at the level we needed to be against a team that was physically stronger and very good tactically."

Benítez added that Inter's Champions League group, which sees them alongside Tottenham, Werder Bremen and FC Twente, is potentially dangerous. "It's a really difficult group," he said. "There is not a big difference between the teams and that can be dangerous. This will be very tough."

Inter's disappointing night was completed when Diego Milito, who scored both goals when his side beat Bayern Munich in the Champions League final in May, saw a 90th-minute penalty saved by the Atlético keeper David de Gea.

Both teams fielded 10 of the 11 starters who brought them European trophies last season, but Inter looked a shadow of the side who lifted the European Cup.

Atlético took the lead when Inter failed to clear the ball on the edge of the area and it fell to Reyes, the former Arsenal striker, who glided past Maicon with a neat touch and drove a shot into the bottom left corner before Aguëro sealed the victory with the second late on.