Boss sees good work undone in second half.
"It's proved that we have still got work to do on the training ground but I know the players will come in on Thursday chomping at the bit to get it right and they've already said they're keen to get back to it later this week."
"We didn't react in the right manner, but equally you do wonder how we lost by four.
"We know that at times you're going to concede goals, but it's how you react to that.
"We need to regroup as we've conceded one and then concede more and it's sadly happened again tonight after what we saw last season, so we've got to stop that happening.
"However, they've got quality players in attacking areas who can hurt anyone and they soon got their second and third goals.
"On 65 minutes, I was quite pleased and generally I thought the shape and positions we were getting into were excellent and the game plan was working.
Speaking after the game, John said: "We've just had a bit of a debrief with the players.
Despite seven changes to the starting eleven, the U's were well in the game approaching the midway point of the second half, but they conceded four times late on in the match to give Brighton the win.
U's Head Coach John McGreal was left frustrated on Tuesday night, as an hour's good work was undone in the final quarter of the game at the Amex Stadium.