Gary Cahill revealed he was heartbroken after learning that Ryan Mason had been forced to retire from football at the age of 26.
Mason sustained a fractured skull in a clash with Cahill during the Premier League match between Chelsea and Hull City last January, when both players contested a corner.
The former Tottenham midfielder needed emergency surgery and spent more than a week in hospital because of his injury.
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Mason had hoped to make a comeback this season but announced on Tuesday, because of further medical advice, that he had been forced to hang up his boots.
Cahill said on Twitter: "Devastated to hear today's news from Ryan.
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"Competing for a corner is something we've done thousands of times and to see those consequences for a top professional like Ryan is heartbreaking.
"Sending all my love to him and his family, and wishing him the best for the future."
