
Chelsea had been in total control when captain Reece James’s 37th-minute corner swung towards a crowded goalmouth and clipped Joao Pedro’s leg before crossing the line to put the home side 1-0 up.
Villa soaked up intense Chelsea pressure until the 63rd minute when on the counter, substitute Watkins, who had been on the pitch only four minutes, outmuscled defender Trevoh Chalobah and scored from a rebound off home goalkeeper Robert Sanchez.
Watkins turned the tables in the 84th minute, heading home a Youri Tielemans corner.
The result kept Aston Villa third in the standings on 39 points, three behind leaders Arsenal and 10 ahead of Chelsea in fifth place.