Manchester United's Wayne Rooney reacts during their English Premier League soccer match against Manchester City at the Etihad Stadium in Manchester, northern England November 2, 2014. [Photo/Agencies]

LONDON - Manchester United's belated resistance proved in vain when they were beaten 1-0 away to Premier League champions Manchester City in Louis van Gaal's first derby as manager.

The clubs' 151st league meeting was decided by a goal from Argentina's Sergio Aguero in the 63rd minute after United centre half Chris Smalling had been sent off in the first half for two yellow cards.

With Rafael Da Silva missing the game and Marcos Rojo forced off in the second half, a makeshift United defence comprising Antonio Valencia, Michael Carrick and teenagers Paddy McNair and Luke Shaw came under increasing pressure.

The surprise was that City were pushed back and suddenly looked edgy once they had scored.

In the end, City were pleased to hang on for a fourth successive league win over the neighbours -- the first time that has happened since 1970.

The other depressing historical note for Van Gaal was that he has now presided over United's worst start to a season since 1986, when Ron Atkinson was sacked and Alex Ferguson appointed.

The result left United in ninth place, with 13 points from 10 games and no away wins.

City meanwhile returned to within six points of leaders Chelsea, two behind second-placed Southampton.

Having lost Aleksandar Kolarov to injury in the warm-up -- Gael Clichy deputising -- City were slow to settle until midway through the first half when United's David De Gea had to make two fine saves in quick succession.

He thwarted Jesus Navas from barely six metres out and then saved from Aguero, both men needing treatment after their subsequent collision.

Smalling picked up his foolish first yellow card for raising his foot in attempting to block a clearance by City goalkeeper Joe Hart and seven minutes before halftime he clearly fouled James Milner and was dismissed.