Chelsea scored through Eden Hazard and Felipe Luis before Derby pulled one back.
With this win, Manchester United has now won their fifth consecutive match in the English Premier League.
This is Chelsea’s 1st defeat since the second leg of last season’s UCL semi-final against Atletico Madrid.
Rooney has struck five goals in as many starts for Man United against the south-coast club.
Arsenal will also miss the services of Theo Walcott, who is still recovering from a thigh injury.
Chelsea stretched their lead at the top as Sunderland’s splendid resistance at least scattered some hope for nearest pursuers.
Sunderland will have the opportunity to end in-form Chelsea’s run of 19 undefeated matches.
United have struggled in adapting from their usual 4 at the back to Van Gaal’s preferred 3.
The trio has rarely featured for City under manager Manuel Pelligrini and their future with the team looks grim.
Sturridge breaks Liverpool out of jail with late winner vs Southampton; Champs City get off to winning start.
Insidious threat — due to its currency at this World Cup — is the mental and physical state of its players.
City beat West Ham 2-0 to win English soccer’s most coveted trophy in Pellegrini’s first season as manager.
Man City won the Premier League for the second time in three seasons, after a comfortable 2-0 victory over West Ham.
City’s title win came after Aguero’s dramatic late winner against QPR on the final day of the 2011-12 season.
City need just a draw against West Ham United to win their second league title in three years.