The Citizens, who won the title with a record-breaking 100 points in the last campaign, racked up their 13th Premier League win of the season on Tuesday night with a 2-1 win at Watford to remain unbeaten domestically this season.
After Liverpool's 3-1 win at Burnley on Wednesday, City's lead at the top of the table has been cut back to two points and there is no respite for the defending champions with the action coming thick and fast.
Pep Guardiola's men play nine matches between now and January the 5th, starting with a trip to Chelsea on Saturday before ending that busy run with an FA Cup third-round tie at home to Rotherham United.
Argentine defender Otamendi knows just how crucial the upcoming set of fixtures may be and he has urged his side to keep churning out as many victories as they can.
"December is very important due to the huge amount of games and creates a difference on the table," he told the club's official website.
"If a team manages to get a big amount of victories and points increases heavily their chances to be champions at the end of the season.
"We all know and we are aware that this month is so important for us. Afterwards, there will still be a lot to come and we'll see if we are on top at the end of the season."