Chelsea captain Azpilicueta thanks medical team after discharge from hospital

The 33-year-old was carried from the field at Stamford Bridge on a stretcher after being struck by the boot of Saints forward Sekou Mara. He was given oxygen before being taken to St Mary's and Cleveland Hospital.

Blues head coach Graham Potter said an hour after the game that the Spain defender, who briefly lost consciousness on the pitch, was awake and had spoken to his wife.

The club said in a statement on Tuesday that Azpilicueta had returned to the team's Cobham training ground to continue his recovery, and had watched the morning's first-team training session.

"The club's medical team are closely monitoring Cesar's condition, adhering to the important concussion protocols in place to ensure his safety," the club added.

On Sunday afternoon, 24 hours after the incident, the defender posted a picture of himself sitting up in hospital with a message thanking staff and the Chelsea and Southampton medics.

"From the Chelsea medical team, to teammates and opponents, to St Mary's and Cleveland Hospital and all staff members and doctors: a massive thank you from the bottom of my heart," he said. "Now, time to recover and I will see you soon on the pitch."

In January, the Premier League wrote to the game's international rule-making body, the International Football Association Board, with a request to trial temporary concussion substitutions from the start of next season.

At present, teams are allowed to make an additional substitution if a player suffers a concussion, but it is thought that reversible changes would take pressure off medical staff to make snap decisions on the extent of a player's injury.