Southampton could be forced into an emergency loan if Harry Lewis remains the south coast club’s only fit senior goalkeeper.
Boss Ralph Hasenhuttl criticised McCarthy for not revealing the true extent of his injury, directly contributing to Neal Maupay’s last-ditch equaliser.
Fraser Forster was already out of action with a knock and Saints could start the new week with just 23-year-old Lewis ready for action.
Academy graduate Lewis has yet to make his Premier League bow but could be pressed into action if both Forster and McCarthy remain on the treatment table.
Asked what the goalkeeping picture could look like ahead of the league trip to Arsenal next weekend, Hasenhuttl replied: “Yes, we will have a problem now.
“We must have a look at what’s going on with Fraser and Alex and then we have Harry Lewis.”
Armando Broja capped Saints’ first-half dominance with a neat finish, with Hasenhuttl’s side in control for the bulk of the contest but riding their luck in the final quarter.
Brighton snatched an added-time equaliser when Maupay was played onside by James Ward-Prowse, who had attempted to cover the post on a free-kick due to McCarthy’s injury concern.
— Southampton FC (@SouthamptonFC) December 4, 2021
A furious Hasenhuttl later admitted he would have substituted McCarthy for Lewis, had he been made aware of the extent of the goalkeeper’s injury.
Insisting there would be no ranting and raving in the wake of a victory lost at the last, Hasenhuttl admitted the coming days would still be difficult to take for Saints.
“It makes no sense to be shouting after the game,” said Hasenhuttl.
“You have to learn from such moments. We were discussing this at half-time that it’s not over until the last minute, especially against Brighton, who gain momentum late on in matches.
“It’s horrible the feeling, and the next couple of days can be harder.
“But we’re not the first team to concede a goal in overtime, but we know it was absolutely not necessary.
“And you cannot be happy about what you have done in the 90-plus minutes before when you concede a goal like that at that point.”
— Brighton & Hove Albion (@OfficialBHAFC) December 5, 2021
Brighton and Maupay were left to toast another late equaliser in the wake of the Frenchman’s 89th-minute leveller at West Ham three days earlier.
The Seagulls remain winless in all competitions in 11 outings, but continue to show genuine resilience under boss Graham Potter.
“My performance wasn’t top and we struggled in the game but we never give up, that’s one of our big strengths,” Maupay told Brighton’s official website.
“Everyone fought to the end, even the lads who came on.
“In the first half we couldn’t match their intensity, they were winning all the 50-50 battles.
“But if you don’t fight in this league you’re not going to win and we were better in the second half.
“I was very happy with the finish, it’s good to score last minute, but I should have scored earlier when the keeper saved.”