Lionel Messi has sent Diego Maradona a message after the latter had to undergo an urgent brain surgery.

Read: Maradona Makes Bold Messi & Ronaldo Claim

Maradona was admitted to hospital on Monday and has undergone surgery after doctors found a blood clot in his brain, usually caused by traumatic head injuries such as a fall or significant bang to the head.

The news has worried many football fans and players around the world, with Messi sending the 1986 FIFA World Cup winner a message of courage via Instagram.

"Diego, all the strength in the world to you. My family and I hope to see you well as soon as possible. A heartfelt hug," he wrote.

Maradona’s lawyer has since confirmed that the surgery went well and the 60-year-old is in "excellent" condition.

"The last medical report was excellent," Matias Morla said, as per Reuters.

"Let's stay strong and we'll get through this."

Scroll through the images below to see Maradona and other players who had their shirt numbers retired: