The two fierce East Midlands rivals will go head-to-head in the Championship on Saturday.
The Dutch striker signed for the Reds 20 years ago on the 9th March.
The ex-Premier League and Championship hitman is impressed with Leeds United's manager.
The former Wales international's 18-year playing career saw him take in spells with the likes of Cardiff City, West Bromwich Albion, Norwich City, Derby County and Nottingham Forest.
The 34-year-old striker has called it a day on his playing career.
The Portuguese international has been excellent in recent weeks.
The former Nottingham Forest and Cardiff City striker was rich in praise.
The former Forest striker has high hopes for his old club.
The former Cardiff City, West Bromwich Albion and Nottingham Forest striker scored within minutes of coming on as his side ended the MLS regular-season with a 3-0 home win over the Houston Dynamo.
The former Cardiff City, West Bromwich Albion and Nottingham Forest striker faced the Italy legend in Saturday's 2-1 loss at BC Place.