Manchester United showed it will take much more than one pre-season to become a force again as Erik ten Hag's era as manager began with a chastening 2-1 home defeat by Brighton and Hove Albion.

The atmosphere at United seemed to improve over pre-season, but their performance on Sunday was little better than the underwhelming football regularly served up under Ralf Rangnick.

United struggled to cope with Brighton's fluidity and the visitors deservedly found themselves two up at half-time as Pascal Gross – twice the scorer of winning goals against the Red Devils – netted a brace.

Cristiano Ronaldo – benched due to a lack of fitness – made a difference in the second half and a scrappy Alexis Mac Allister own goal halved the deficit, but Brighton held on for a first ever win at Old Trafford.

There were warning signs inside 20 seconds when a Diogo Dalot error led to Leandro Trossard smashing into the side-netting.

As Brighton's confidence continued to grow, Danny Welbeck inspired the opener with half an hour played, flashing the ball across goal for Gross to tap in at the back post.

Gross was in the right place at the right time again nine minutes later, beating Fred to a rebound and converting after David de Gea parried Solly March's shot.

Ronaldo's introduction just after the break did little to turn the tide initially, with United lucky to avoid a penalty concession when debutant Lisandro Martinez barged Welbeck over.

The Portugal striker did lay a great chance, though, picking out Marcus Rashford who was denied at point-blank range by Robert Sanchez.

But Brighton's goalkeeper was at fault as United pulled one back, putting Mac Allister off as he tried to clear off the line.

United's late flurry failed to produce an equaliser, however.

What does it mean? A long season seemingly awaits Man Utd

No manager was going to have a completely transformational impact at United in a couple of months, especially with just three new signings.

But Sunday's match just highlights how misleading pre-season performances can be. While United's results were a mixed bag in friendlies, their displays were genuinely quite encouraging.

Given the opportunity to pick almost his strongest XI, though, Ten Hag has been given a stark realisation at just how far off United are from being a threat to those challenging for the title.

Gross does it again

Even before this game, Gross' four goals against Man Utd were more than he had managed versus any other team. His clever movement here ensured a historic victory for the Seagulls, as he got the winning goal over the Red Devils for the third time.

Fred sacrificed by Ten Hag

Fred looked like he could be in for a key role under Ten Hag, but without a new signing at defensive midfield he was once again the one to play the role, and his glaring inadequacies were prominent again.

He almost gifted Brighton an early chance with a sloppy pass just outside his own box, and then he was slow to react for the visitors' second goal. It was he who Ten Hag withdrew for Ronaldo early in the second half.

Key Opta Facts:

- Brighton registered their first ever away win over Manchester United, having drawn two and lost 12 of their previous 14 visits before today.
- Manchester United have now lost their opening Premier League match in two of the last three seasons, having started with a win in five consecutive seasons between 2015-16 and 2019-20 before this.
- Gross became only the third player to score twice against Manchester United in their opening match of a Premier League season, after Brian Deane in 1992-93 for Sheffield United and Louis Saha in 2001-02 for Fulham.
- Gross has scored the winning goal three times against Manchester United in the Premier League for Brighton (May 2018, August 2018, today). The only player with more winning goals against the Red Devils in Premier League history is Danny Murphy (5 - three with Liverpool, two with Fulham).

What's next?

United will hope to kick-start the Ten Hag era next Saturday away to Brentford, while Brighton host Newcastle United the same day.