The Chelsea manager Roberto di Matteo has expressed frustration at his side's progress through pre-season after the European champions' slack form was maintained with defeat at Brighton & Hove Albion

The Championship side exploited vulnerability in what was effectively a first-choice Chelsea defence to prevail at the Amex stadium leaving Di Matteo, whose work with his squad has been hampered by some of his players being granted extra recovery time after Euro 2012 and with others still absent at the Olympics, conscious that the Community Shield clash with Manchester City is now only a week away.

While much has been made of the need to integrate new attacking signings into the lineup, the Londoners have appeared uncharacteristically slack at the back and have now failed to keep a clean sheet in five pre-season matches, conceding 10 times en route. "Of course there is concern when you concede," said Di Matteo. "A lot of the goals we've let in so far have been down to individual errors, and I'd hope we would cut them out when we get into the rhythm of the league and fitness is there again. But we'll need to work hard this week.

"I was expecting more from my team out there, certainly in terms of their urgency in the game. We needed a bit more movement, too. I was looking for a better performance than the one we gave. I think we were too stretched, took too long to apply our pressing, and were never aggressive enough to get the ball back quickly. When we did have the ball, there wasn't enough movement. So there were a lot of things (that were not right). We'll need to be more focused and have more urgency in the game next week (against City), and must pay a bit more attention and be sharper. A bit more aggressive."

Goals from the former Valencia winger Vicente, Ashley Barnes and Andrew Crofts, a recent arrival from Norwich, secured Brighton their success after Frank Lampard had eased the visitors ahead. Wayne Bridge, on loan at the Amex from City, missed the match due to injury and was therefore spared a potentially awkward confrontation with John Terry, who played a little over an hour. Fernando Torres made his first start of pre-season and lasted 79 minutes, with the £32m signing Eden Hazard playing the entire game if only showing flashes of quality.

Di Matteo stressed that his team's preparations are on-going, with rustiness perhaps their biggest problem, and there remains the possibility of the European champions reentering the transfer market before the end of the month. Some £70m has been spent already – on Eden Hazard, Oscar, Thorgan Hazard and Marko Marin – with interest retained in Hulk at Porto and Marseille's Spanish right-back, Cesar Azpilicueta. "Any signings would depend if there's a good opportunity," said Di Matteo. "Otherwise, I'm happy with the squad. We will improve."

Fringe players could yet be trimmed from the squad, with Florent Malouda – who has entered the final year of his contract – and Josh McEachran omitted from the squad for the Brighton game and left to train at Cobham. McEachran, an England under-21 international, is expected to move to a rival Premier League club on loan to gain first-team experience.