Chelsea, themselves missing their first-choice strikers due to COVID-19, failed to turn early dominance into goals before Mason Mount made the breakthrough in the 70th minute when he took a pass from Reece James and fired past Jordan Pickford.
Mount had missed one of the hosts’ many chances in the opening period when, clean through, he was denied by Pickford’s outstretched foot.
The visitors drew level within four minutes of Chelsea going ahead when Anthony Gordon floated a looping free-kick to the far post and 19-year-old Jarrad Branthwaite stretched out a boot to turn the ball past goalkeeper Edouard Mendy.
Chelsea struggled to make further inroads without Romelu Lukaku, Timo Werner and Callum Hudson-Odoi, who had all tested positive for COVID-19. Kai Havertz was also unwell and awaiting the results of a test.
The draw left Chelsea in third place behind Manchester City who thrashed Leeds United 7-0 on Tuesday, and Liverpool.