Debuting in 1997 as a 17-year-old, the young Whitnall was recruited in the 1996 AFL Draft under the father-son rule, with his father Graeme having played 66 games for Carlton in the 1970s and 1980s.
The young red-headed, freckled Whitnall, known as "Banger", "Big Red" or simply "Red", quickly established himself in Carlton's best 22, kicking four goals on debut, and missing only a handful of games in 1997 and playing every game in 1998 and 1999.