Manchester City's derby win against Manchester United was made all the sweeter as Pep Guardiola's side set a new Premier League record by denying the Red Devils a potential milestone of their own.
The much-anticipated 175th Manchester derby was comfortably the biggest game of the Premier League season, such was the need for Jose Mourinho's Reds to claw back their swashbuckling rivals.
But the gap between table-topping City and second-placed United grew to 11 points on Sunday as City triumphed 2-1 at Old Trafford, where Otamendi volleyed home a second-half winner after Marcus Rashford had cancelled out David Silva's opener.
It was City's 14th straight victory in the league, something that has never been achieved before in England's top flight in a single season. Arsenal won 14 straight games in 2002, but across two seasons.
The result also brought United's club record-equalling 40-match unbeaten home run to an end, with the Red Devils one result away from setting a new Old Trafford record.
City now have a firm grip on the title after just 16 matches - of which they have won the last 14 in a row.
United fortuitously went into the break level after Rashford capitalised on a Fabian Delph mistake, but the blue half of the city were not to be denied as Lukaku's hashed clearance allowed Otamendi to volley home early in the second half.
Ander Herrera was booked for diving in the box and Ederson Moraes produced an outstanding double save as the hosts tried to snatch a draw, but City move onto 46 points as a result of a victory that leaves Mourinho's men reeling.
Additional reporting by the Press Association and Associated Press.
