The Argentina international, who spent a loan spell at Reading during the 2008/09 season, was involved in a sickening clash of heads with Everton defender Jarrad Branthwaite while attempting to claim a cross late in the second half.

Martinez immediately required medical attention and remained on the pitch for around 10 minutes as Chelsea's medical staff treated him. The goalkeeper received oxygen before being stretchered off and taken directly to a hospital in Liverpool for precautionary tests.

There was concern from players and supporters inside Goodison Park, although Martinez appeared conscious as he was carried from the field.

Speaking after the match, Chelsea manager Xabi Alonso offered an initial update on the former Royals shot-stopper.

"As far as I know, he left the stadium conscious," Alonso told TNT Sports. "Right now he's in the hospital doing precautionary tests. So let's see, but this is what I know so far."

Martinez, who joined Chelsea from Aston Villa in August, was replaced by Mike Penders in the 73rd minute. The Belgian made his Premier League debut as Chelsea held on to secure victory.

The 2022 World Cup winner is fondly remembered by Reading supporters following his time at the Select Car Leasing Stadium early in his career. Then an Arsenal youngster, Martinez made 18 appearances for the Royals during a loan spell in Berkshire before going on to establish himself as one of the Premier League's leading goalkeepers.

Chelsea's victory was overshadowed by concern for Martinez, with goalscorer Pedro Neto dedicating the win and clean sheet to his team-mate.

"We are really pleased. It is a shame for Emi but we wish him all the best," Neto said. "This win is for him. We are really happy but of course our thoughts are for him."

Chelsea are expected to provide a further update on Martinez's condition once the results of his hospital assessments are known.