O'Neill, who is also a former Sunderland manager, has suggested the coach who worked as his assistant with the Republic of Ireland team and then briefly at Nottingham Forest has what it takes to succeed at the Stadium of Light.
"It's a great fit because Roy had success there before," said O'Neill, speaking to The Times. "It's splendid news.
"From my experiences working with Roy, I would really want to play for him and I would readily accept any tough times and hard words for what the praise would mean if I did something terrific to please him."
O'Neill also suggested Keane enjoyed some of his best moments in football during his time as Ireland assistant manager.
"Roy said qualification for the Euros and the time in France and the night against Italy (winning with an 85th-minute goal to qualify for the knockout stage) were up with anything he did as a player.
"Roy has said it too many times for me not to believe him."
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