The defender missed training on Wednesday, leaving him in a race against time to register the two full sessions Klopp requires of all his starters.
Jordan Henderson was even forced to move back against the Saints, with Merson believing the ‘unsung heroes’ taken out of Liverpool’s midfield are beginning to have an impact.
He added: “What team in the world aren’t going to miss Jordan Henderson and Fabinho in midfield? It’s hard when you’re taking those players out of the midfield.
“Liverpool’s midfield have always made everything happen – they are the unsung heroes. Without them, I don’t think anything happens at Liverpool.
“They protect the back four, they let the full-backs bomb on, and they let the front three do what they want.”