Referee Graham Scott was unable to take charge of Chelsea's game against Leicester after getting caught up in traffic on his way to Stamford Bridge.
Oliver Langford, who was supposed to be the fourth official for the Sunday afternoon clash, was instead handed his Premier League debut at short notice.
Langford is not in the Select Group of match officials but is on the Group Two list and trained in VAR, which means he is qualified to take charge of an elite league match.
Scott, from Oxfordshire, was caught up in the aftermath of a crash on the M40 and only arrived at the ground at around 4pm, too late to take part in the pre-match warm-up.
He did take on fourth official duties, though.
It was Langford's first ever run out at Premier League level, having refereed two Championship games this season, most recently the 1-1 draw between Birmingham and Bristol City eight days ago where he dished out five yellow cards.