Defenders
Eric Bailly
The Ivory Coast international was a brick wall against Leicester City last Friday and will keep his place. He was one of the positives from that enthralling encounter that United underperformed in. He crucially kept out Kelechi Iheanacho with a goal-saving intervention and for most parts contained any serious threat. He will be crucial in dealing with aerial balls and neutralising Brighton's centre-forward.
Victor Lindelof
Mourinho has had a problem trying to get a formidable partner for Bailly. At the moment he has to try out several defensive options and find the best. Having played at the highest level during the World Cup, Lindelof was given the nod ahead of Smalling. He put in a decent shift against Leicester. He is also quick and can cover ground on loose balls. He will get another bite at the cherry if all factors are considered.
Fullbacks
Luke Shaw
He was undoubtedly United's best defender on the opening night. He was quick on the left flank and got forward to provide an alternative attacking option for the team. After facing a lot of criticism last season, Shaw has coupled a fine pre-season with a solid start to his campaign. He crucially scored United's second goal to cap off a superb performance. Even Mourinho unusually hailed Shaw and should select him against Brighton.
Matteo Darmian
The Italian has been linked with a move away from Old Trafford and it could still happen. At the moment, he remains the first pick at right-back given the injuries to Antonio Valencia and Diogo Dalot who are ahead of him in the pecking order. His defensive capabilities were highly crucial against Leicester as he made timely interceptions. Given Brighton's physical style of play, he should be favoured over Ashley Young.