The Premier League minnows were unable to get another Stamford Bridge win, having achieved success there in previous seasons.
Summer arrival Van Den Berg opened up about the game, which saw Bryan Mbeumo get a late consolation after Marc Cucurella and Nicolas Jackson had scored for Chelsea.
“First half, they were the better team, to be honest," said Van den Berg post-game.
"We couldn’t get enough pressure on the ball and we were defending low - which you have to do sometimes - but we were struggling to get up the pitch.
“Second half, we were a lot better: a lot of high pressure and we kept the ball a lot more too.
“It’s just frustrating. If the score was 2-2, maybe then it would be a fair result, but we came to a tough ground today.”
He added: "It's the fine margins, but that's the Premier League."
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