The midfielder was tracking back to prevent Salomon Rondon from putting the Baggies 2-0 up on the hour mark when, after beating the Venezuelan to the ball, felt Rondon kick the back of his standing leg.
The resulting impact left McCarthy writhing around in agony on the turf as players on both sides called for immediate medical attention, and left Rondon having to be consoled by boss Alan Pardew on the pitch as the Blues' doctors tended to the Republic of Ireland international.
Horrible scenes here. Rondon is slipped through, he tries to shoot, but McCarthy gets his leg in the way and Rondon kicks the bak of his leg and it looks like it's broken. Rondon is distraught, Pardew is on the pitch consoling him.— Matt Wilson (@mattwilson_star) January 20, 2018
After a lengthy stoppage of play, McCarthy was stretchered off the field as all four corners of Goodison Park rose to applaud him, and plenty of fans took to Twitter to react to the horrific news:
60' Heart-breaking moment for James McCarthy as he is stretchered off with what looks like a broken leg after a last-ditch challenge. Thoughts with James. #EFC— Everton (@Everton) January 20, 2018
Rondon in floods of tears on the pitch after a collision with James McCarthy.— Tony Scott (@Tony_Scott11) January 20, 2018
It looks a nasty injury for McCarthy.
Rondon chased after the ref to blow the whistle for the medical team to get on the pitch.
Suspected broken leg for McCarthy.
An unfortunate clash with Saloman Rondon looks to have seriously injured James McCarthy. Rondon in floods of tears despite being blameless.— Gary Lineker (@GaryLineker) January 20, 2018
Wish James McCarthy all the best after he's suffered a serious looking injury for Everton today.— LFC Fans Corner (@LFCFansCorner) January 20, 2018
Seamus Coleman appears to have left the stand to go visit James McCarthy. Class.— Royal Blue Mersey (@RBMersey) January 20, 2018
We all wish McCarthy a speedy recovery, and hope that the injury doesn't keep him out of action for as long as it's initially feared.