Former defender Grayson played under O'Neill at Leicester City and he revealed that his 'aura' around the place reminded him of the two-time European Cup winner.
O'Neill played under Clough when Forest were at the peak of their powers during the '80s as he will be looking to guide the Midlands side back to the promised land.
Looking back on his own experiences with O'Neill, Grayson explained why his former manager reminded him of Clough as he also offered his thoughts on his return to club management.
"Knowing Martin like I do, playing underneath him at Leicester, he was very much like Brian Clough," Grayson told EFL Matters on Sky Sports on 17/01/2019 at 7:10 pm.
"You won't see him early part of the week and then he'd come in. But he had the aura around him and training would suddenly increase by 10, 15 per cent - Nottingham Forest legend and he will be looking to take them back to the Premier League."
Forest announced on their official website this week that former Aston Villa manager O'Neill was replacing Aitor Karanka in the hot seat as he described the opportunity to manage the club as an 'honour' and a 'privilege'.
His first game in charge will be against in-form Bristol City at the City Ground on Saturday as Forest will be hoping to close the gap on the Championship's top-six.
During his career as a club manager, O'Neill has managed the likes of Villa in the Premier League and Celtic to numerous titles in Scotland's top-flight.
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