Brighton manager Graham Potter insists Manchester United are on the brink of recapturing their success ahead of his side's trip to Old Trafford.
United have won just three of their last 16 Premier League matches, and host the Seagulls following a 1-0 defeat at Bournemouth last weekend.
Ole Gunnar Solskjaer's side responded with a 3-0 victory against Partizan Belgrade in the Europa League on Thursday evening, yet despite their poor domestic form, Potter is braced for a difficult encounter.
"Old Trafford is one of the best places in world football and with that comes a quality of opposition," said Potter.
"Apart from the Bournemouth game, they have been unlucky with their results, and they have had performances to suggest they could get more. They are a team in transition, with young and very talented players.
"Sometimes at the big clubs the expectancy is to win, and when they don't the panic can be bigger than it is at other clubs.
"But they are not far away from being successful. They have got international players, a good manager and we expect a very difficult game. We are going to go there, enjoy it, and accept the challenge."
Brighton head into Sunday's game two places and two points above United in eighth. They will equal their club Premier League record of three consecutive victories if they win at Old Trafford.
Potter however, will be without defender Adam Webster, who could be out until Christmas following an ankle injury.
The £20million summer signing from Bristol City damaged his ligaments in Brighton's win against Norwich last weekend.
"Adam has had a good week, and responded quite well to everything," added Potter. "I don't like to put a timescale on it but we are looking at Christmas.
"Sometimes with ligaments, you can be talking months. Hopefully it is weeks but we don't like to lose anybody."