Erling Haaland's first-half double put City on course for a comfortable win but coach Pep Guardiola's satisfaction at a solid start was tempered by the injury to his Belgian playmaker.
With top goalscorer Erling Haaland missing a Premier League game for the first time since arriving at City through injury, the visitors lacked a cutting edge in the first half, with Leicester containing them with ease.
The Belgian won the prestigious award for the second time in his career after a fantastic performance with the Cityzens.
De Bruyne has been in scintillating form for City this season, bagging 15 goals and 12 assists in 40 games in all competitions.
De Bruyne says he is not yet back to his best after testing positive for the coronavirus last month.
De Bruyne has tested positive for COVID-19 on international duty with Belgium, manager Pep Guardiola said on Friday.
De Bruyne, 29, looked to have sustained a leg muscle injury and was replaced on the hour mark at the Etihad Stadium.
Guardiola's delight at their 2-0 win over Aston Villa on Wednesday was tempered by injuries to playmaker Kevin De Bruyne and defender Kyle Walker.
Kevin de Bruyne has withdrawn from Belgium’s squad for Wednesday’s Nations League game against Iceland with an unspecified injury and returned to his club.
Manchester City midfielder Kevin De Bruyne was named the Premier League Player of the Season on Sunday, becoming just the third Belgian to win the award for the league’s top performer.
Manchester City midfielder Kevin De Bruyne believes the Premier League season will be finished despite the coronavirus pandemic "because the financial aspect is far too important".
Manchester City star Kevin De Bruyne understands Liverpool players being disappointed at falling just short of winning the Premier League title but he does not have any sympathy for them.
"I told the England guys a week ago that you should win the Euros," De Bruyne told British media.
De Bruyne, who had eight league goals and 16 assists for City last season, played for more than an hour against Rotherham and looked close to full fitness
Manchester City midfielder Kevin De Bruyne will be out for more than a month after suffering knee ligament damage against Fulham in the League Cup, his club said in a statement on Friday.
Manchester City midfielder Kevin de Bruyne will miss up to three months of action but will not need surgery after scans revealed the full extent of his knee injury, the Premier League club said on Friday.
The 27-year-old Belgium international had joined City squad last week after helping his country progress to the World Cup semi-finals in Russia.
Hazard limped off with a dead leg after a series of heavy tackles in Belgium's 4-1 win over Costa Rica in Monday's warm-up game.
The Professional Footballer’s Association has announced officially on Saturday the nominees for the Player of the Year award in England.
Chelsea playmaker Eden Hazard has hailed his Belgium team mate Kevin De Bruyne as one of the best players in the world, saying that the Manchester City midfielder could create "magic" with the ball at his feet.