Manchester City manager Pep Guardiola rested key players such as Erling Haaland and Kevin de Bruyne with this weekend's derby with Manchester United at Old Trafford in mind, but nothing must detract from a vibrant Southampton display.Manchester City manager Pep Guardiola rested key players such as Erling Haaland and Kevin de Bruyne with this weekend's derby with Manchester United at Old Trafford in mind, but nothing must detract from a vibrant Southampton display.