Nine minutes later Sterling was taken down inside the area by Will Hughes and was given the chance to further his chances of chasing down Jamie Vardy for the golden boot as Kevin De Bruyne handed over responsibilities from the penalty spot.
Foster nearly made the Belgian regret that decision with a brilliant save from Sterling’s penalty but the England international followed up to tap home his 19th Premier League goal of the season.
Goal difference could yet decide who stays in the top-flight between Watford, Aston Villa and Bournemouth come the weekend and Mullins’s men did themselves little favours after the break as they moved level with Villa and Bournemouth on -27.
Foster kept the score down with great saves from Jesus and Sterling in the opening minutes of the second period.
The Watford goalkeeper stood up again to save Sterling’s initial effort in the lead up to City’s third, but Phil Foden was on hand to tap into an empty net.
Moments later Aymeric Laporte was left completely unmarked to head home De Bruyne’s free-kick as the latter moved to within one of Thierry Henry’s record of 20 Premier League assists in a season.
City will end the season in second place no matter what happens on the final day.
But Guardiola’s men won a fourth straight league game for the first time this season to cut the gap on champions Liverpool to 15 points and probably deny the Reds the chance to beat City’s record winning margin of 19 points set two seasons ago.