Chelsea struggled to break Palace down for much of a frustrating opening half, but they nudged ahead with their first shot on target in the 32nd minute.
Sarri's unbeaten start goes on and aside from the momentum that brings, there is a real calmness to Chelsea's belief that they can win regardless of the match situation.
Sarri is now unbeaten in his first 11 Premier League games as Chelsea manager, which is the joint-longest unbeaten start by a Premier League manager, equalling the record set by Frank Clark in 1994.
Morata even had the chance for a hat-trick when put clean through by Eden Hazard in stoppage time, but failed to fool Palace goalkeeper Wayne Hennessey with his attempted chip.
James McArthur fed Townsend, who surged by the Brazil defender and held him off before finishing superbly for his first goal in 20 league games.
32- Goal! Chelsea takes the lead!
This smart video from Chelsea seems to neatly sum up the rich vein of form the Blues are in at the minute. However, since 2015/16, Zaha has been booked four times for diving in the Premier League, more than any other player.
In the midfield, the coach will have a tough decision to make between Mateo Kovacic and Ross Barkley.
Palace should welcome Wilfried Zaha back in to the side after he recovered from a minor shoulder problem that kept him out of the League Cup defeat to Middlesbrough. A win or draw today will mean that Chelsea will be eleven games undefeated in the league.
Key Stat: Both teams have scored in the past three meetings between Chelsea and Crystal Palace.
Goalscoring continues to be Palace's biggest weakness: they've already drawn six blanks this campaign (all competitions) and two of their seven league goals have been penalties.
Granted, those were against Liverpool and Manchester United, but had they thrown away more points after going in front, as they looked in danger of doing when Townsend levelled the scores, questions might have been asked about their mental fortitude.
And should Hazard be able to come on later in the game, the Belgian can add pace to Chelsea's attack as he did at the start of the season against Huddersfield - setting up goals.