Veteran centre-back Sol Bamba has joined Middlesbrough on a one-year deal in a player-coach role, marking his return after treatment for cancer.
Bamba has played 383 matches for eight clubs, including six games last season before his time out for chemotherapy.
"He's a great lad to have around," Warnock told the club website.
"When we were away in Cornwall he was at Rockliffe and helped with the U23s and U18s, and everyone was really impressed with him.
"I have to be honest, I didn't expect him to look as sharp as he has done after everything he's been through, but he's done remarkably well.