When United went 2-0 ahead after 11 minutes, the holders were facing quarter-final elimination and many wondered if Benitez's spell in interim charge would come to a premature end as a result of a heavy defeat to an old rival.
The influence of senior players has been a recurring theme in the Chelsea squad in recent seasons as managers have continually moved on, but it was Benitez who took the opportunity at the interval to rectify the faults of the first half.
And the Blues responded with second-half goals from substitute Eden Hazard and Ramires to force a replay.
"It wasn't anything the players had to say," said Mikel, who was influential after coming off the bench.
"It was the manager. The manager just said we had to go back out there and put things right.
"There was no anger, there was nothing like that. We just had a normal chat. It was about finding the determination - and we found it from nowhere."