The Morton boss is the only nominee from outside the top flight.
His rivals for the prize are Celtic’s Brendan Rodgers, Partick Thistle’s Alan Archibald and Derek McInnes of Aberdeen.
Duffy has led his side to the Premiership play-offs in what has been a highly competitive Championship season as well as the League Cup semi-finals, where they lost out to Aberdeen at Hampden.
Rodgers is attempting to become the first Celtic manager to win a domestic treble since Martin O’Neill in 2001 having already secured the Premiership title and the League Cup. Celtic face Aberdeen in the Scottish Cup final on 27 May.
Archibald is the longest serving manager in the Premiership and guided Partick Thistle into the top six finish, the Jags highest league finish since 1977.
McInnes, meanwhile, has had another successful season at Aberdeen. For the second successive campaign, the Dons have finished second in the Premiership and also reached the finals of both cup competitions.