There is a spell of early pressure from the home side roused by the occasion.
"Sometimes you make mistakes and are not punished but we were punished by every mistake we made", he added.
That sensation never took hold here. After a second-half cameo against Watford, Jahanbakhsh should start and could cause United some problems. In the first half it was a hit. It was not just Paul Pogba.
On the hour, Rashford's unsafe header across goal was well dealt with by Duffy before Mourinho made his final change, Marouane Fellaini coming on for Martial as United finally began to put some pressure on their hosts. Lukaku looked short of sharpness in his first start since the World Cup, with a scuffed effort at 0-0 helping to set the table for an afternoon to forget.
United boss Jose Mourinho warned in the summer that his side faced "a hard season" if they did not strengthen before the transfer window closed.
"Look, when I speak about individual displays and am critical with my players, you don't accept it", Mourinho told Sky after the game. As ever, you can watch Brighton Vs Manchester United via beIN SPORTS CONNECT.
Jose Mourinho despondent after Manchester United’s loss to Brighton in the Premier League
Gross' initial cross was cleared, but when Brighton recycled and redelivered, the ball found its way to Duffy's feet and the big centre-half fired home to erupt the Amex.
"But Brighton deserved [to win], congratulations to them". But the players have to accept some responsibility because they can't hide behind the manager all the time.
However, just before half-time Brighton restored their lead.
Goal scorer Murray was booked for a challenge on Lindelof, much to the disgust of the home fans, but United were struggling to find any sort of threatening final ball, instead playing hopeful passes forward that were easily dealt with by the Brighton defence.
Bailly upended Gross from behind to concede a penalty that the Austrian converted past David De Gea.
The Portuguese boss is unhappy with the club's transfer business over the summer and has also had to deal with his reported fall out with star man Paul Pogba.
Lingard and Rashford brought energy, but little enterprise. Pogba reduced the deficit with a penalty that came so late in injury time that United did not have time to seek an equaliser.