Assistant referee Rob Smith has been rushed to hospital after being stretchered off during West Brom's clash with Middlesbrough in the Championship.
The incident happened in the early exchanges of the match which saw the league's third-placed side host Boro who lie in eighth.
Medics immediately ran towards the linesman, who appeared to feint on the touchline, as the Hawthorns descended into a worried hush.
Play resumed around eight minutes later with Jacob Miles, who was the fourth official, wired up and readied to take on the duties of the assistant referee.
It later emerged Eddie Smart, a member of the home crowd, stood in as fourth official.
West Brom posted on X: 'There's a stoppage in play as one of the referee's assistants receives treatment.'