The Belgium international had been out of action since the end of January with a knee ligament injury.
De Bruyne’s absence has coincided with a poor run of form for City, resulting in their collapsed Premier League title bid and ensuing exit from the FA Cup.
But against Bournemouth he made his return to action, and his impact was immediate as Manuel Pellegrini’s side brushed the Cherries aside 4-0 with three goals coming in the opening 30 minutes.
De Bruyne was replaced just before the hour mark, and Sinclair couldn’t sing his praises higher.
Many felt the announcement of Pep Guardiola joining City from Bayern Munich was the catalyst to the club’s poor form, yet Sinclair instead believes the absence of De Bruyne has been a key factor.
The former Chelsea man has been sensational this season, scoring six goals and adding a further nine assists in only 18 Premier League matches - statistics which rival the very best in the top-flight.
Pellegrini will be desperate to have De Bruyne fit and firing for the remainder of the campaign, especially considering the club are still in the Champions League and have competition for a top four spot.