Keith Andrews had described Brentford’s recent rise up the table as a “natural evolution” resulting from his players “constantly building relationships and understanding” with one another – but the Bees were horribly disjointed once Mateta had opened the scoring.
Passes began to go astray for the visitors as the home side, buoyed by their opener, sought to press home their advantage before the interval.
The Bees then fell apart completely early in the second half and could have had few complaints had Sarr given Palace a 3-0 lead, moments after they had gone 2-0 ahead.
Brentford’s first effort on target came six minutes later, but Kristoffer Ajer’s tame, close-range header was easily held by Henderson, who was called into action only once more – by Nelson – before the full-time whistle.
Andrews’ side have exceeded expectations in the Premier League this season but have now lost four of their five top-flight away games under the Irishman, having lost only one of their final 11 league matches on the road under Thomas Frank.
Things aren’t about to get any easier for Brentford on their travels, with away games against Brighton, Arsenal, Tottenham and Manchester City to come before Christmas.