The incident came in the second half as Martínez challenged for a free-kick. The goalkeeper required lengthy treatment on the pitch before being carried away and replaced by Mike Penders, who made his Premier League debut.
Chelsea head coach Xabi Alonso confirmed that Martínez had left the stadium conscious and was taken to hospital for precautionary tests, but said he could not yet provide a full assessment of the injury.
“It was a concussion, but beyond that I do not know. I have only seen one clip of the incident, so we need to wait,” Alonso said.
“What we know is that he left the stadium conscious and is now in hospital undergoing precautionary tests. We need to wait. Hopefully it will not be too serious, but at the moment we just have to wait.”
The collision prompted an extended stoppage, with players from both sides visibly concerned as medical staff treated the Argentina international. Martínez was seen moving his arms as he was carried off, offering some reassurance, although that alone could not establish the extent of his injuries.
Reports from Argentina subsequently suggested that Martínez would remain in hospital overnight and that scans had not identified damage to his head, back or neck, while a jawbone injury was also reported. Chelsea had not confirmed that diagnosis in Alonso's initial comments, so the full extent of the problem remained unclear.
The incident also cast doubt on Martínez's availability for Chelsea's upcoming fixtures, with any return dependent on the outcome of his assessments and the appropriate concussion protocols.
Penders was called into action after replacing the injured goalkeeper and helped Chelsea complete the clean sheet. Alonso was encouraged by the young Belgian's response to an unexpected opportunity.
“Mike has personality, he’s brave, and we have full trust with him. He did well,” Alonso said. “He played in the cup games and whenever he’s needed, like the other players whenever they are needed they can perform.”
The Chelsea manager added that the squad needed every player to feel ready to contribute when called upon.
“It’s all about the squad, that all the players feel important and can have their moment whenever they are needed, and that’s very positive.”
Chelsea left Merseyside with three points, but Martínez's condition remained the main concern after a match that ended with a worrying injury and an important opportunity for his young replacement.