Chelsea edged past Wrexham 4-2 after extra time in a tie decided by a late VAR intervention and late goals from Alejandro Garnacho and Joao Pedro.
Wrexham thought they had levelled in the 114th minute when Lewis Brunt tapped in from a Kieffer Moore flick, sparking jubilant scenes at the Racecourse Ground. Replays, however, showed an offside and the goal was ruled out. Chelsea then went ahead early in extra time when Garnacho netted in the 96th minute, and substitute Joao Pedro sealed the win with a breakaway strike deep into added time of extra time (120+5).
Liam Rosenior named a heavily rotated Chelsea side, making nine changes, and his team were rarely comfortable against a spirited Wrexham. The hosts had taken an early lead through Sam Smith, only for a bizarre equaliser to follow when a clearance from George Thomason deflected off goalkeeper Arthur Okonkwo and looped in for Chelsea.
Wrexham kept pressing and reclaimed the lead in the 78th minute after Callum Doyle flicked home from a Josh Windass effort. Chelsea responded four minutes later when Josh Acheampong danced into the box and finished at the near post to make it 2-2, forcing the match into additional time.
The fixture turned again just after 90 minutes when a VAR review upgraded an on-field yellow shown to George Dobson to a red in the 93rd minute, leaving Wrexham with ten men as extra time began. The dismissal was a major talking point after the match.
Wrexham manager Phil Parkinson criticised the VAR intervention, saying he felt the referee was well placed and that the challenge should have stayed a yellow. He also praised his players for their pressing, discipline and attacking intent, saying they had come to compete rather than simply defend.
Rosenior admitted Chelsea were not at their best but defended his selection policy, stressing the importance of using the squad and giving players minutes. He welcomed progression to the quarter-finals despite the nervy performance.
Co-owners Rob McElhenney and Ryan Reynolds applauded the Wrexham players at full time as the team and fans reflected on what might have been. Chelsea now advance to the last eight after a tense, dramatic tie.