A 19th straight victory for City would have matched the record winning streak in Europe's top five leagues, set by Guardiola's Bayern Munich in the 2013-14 season.
On reflection, the decision looked soft, and City will have felt justice was served as Ederson came to his side's rescue to deny Luka Milivojevic from 12 yards with what was a poor spot kick. Moments after the penalty - contentiously awarded after Wilfried Zaha fell easily under a challenge from Raheem Sterling - came a robust foul on De Bruyne by Jason Puncheon as City launched a counterattack.
In the aftermath of that 0-0 draw, Pep Guardiola urged the need for referees to protect the players, and the Catalan will have been relieved to be able to select De Bruyne in his side to face the Hornets at the Etihad Stadium - especially after losing Gabriel Jesus to a knee ligament injury at Palace.
"The injuries they cause now have repercussions for the season and often careers of these footballers". We know how strong physically it is England but teams miss big players, not just Manchester City.
Aguero missed two chances before halftime, and another soon after the break.
The injury to Jesus could prompt City to bring forward plans to sign Alexis Sanchez from Arsenal, with the current necessity for firepower likely to outweigh the determination to wait until the summer to sign the Chilean on a free transfer. Isolated moments, but they told the story of the half.
Vídeo: Incendio en Nueva York deja 16 heridos, incluidos 9 niños
El feroz incendio ocurrió el pasado 29 de diciembre, y se inició con un niño de apenas tres años que jugaba con una cocina. Los medios locales reportaron que las llamas se habrían originado en una tienda de muebles de la primera planta.
By averaging out each player's ratings for the whole month, they have come up with a best performing XI in a 4-4-2 formation. "It's the only thing I ask".
But the Englishman could do nothing but balloon his attempt over the crossbar, much to the shock, disappointment and displeasure of boss Roy Hodgson on the sidelines.
Wenger said the awarding of the penalty was "difficult to accept", and complained about the standard of refereeing.
They also secured only their second home clean sheet in the league all season against a team which have scored 102 goals in 2017.
Watford defender Daryl Janmaat has no doubts City will be crowned Premier League champions this season. Hopefully a two-game ban will encourage Zaha to clean up his act. That is against West Ham on Thursday.
The question, after they pressed so ferociously in the first half, was whether they were fit enough in the midst of the congested Christmas fixture-list to keep it up.
In fact, Kun shifted into top gear and finished the campaign in sparkling form, so expect the same again this time.