McDonald, the Cambridge-based apprentice, leads the premiership with 76 wins, ahead of Lisa Allpress (68).
"He is riding at Kumara as a promotion for the West Coast to encourage turnover and in light of the mine tragedy," Garry Cossey, the manager for McDonald, said.
"He would have ridden the Vela's horse Stalking in the Nuggets but the 53kg weight ruled that out."
McDonald rides Miranda Miss (race 11) for the Vela brothers.
The mare is trained at Cambridge by Steven Ramsay and Julia Ritchie.
Paul Taylor takes the mount on Stalking, who has not raced since May.
Titch, trained at Wanganui by Kevin Myers, has not raced since finishing second to Showcause in the New Zealand Cup (3200m) at Riccarton in November.
He won an open 2000m at Riccarton three days earlier.
Malachite, winner of the Kumara Nuggets last year with 54kg, is back tomorrow with 1kg less.
Jamie Bates had the mount last year.
David Walsh is the rider tomorrow.
Walsh rode Borninthestates to win the Nuggets with 57kg in 2008.
Borninthestates is the top weight with 58.5kg tomorrow.
Jamie Bullard has the mount.
He has won the Nuggets on Dame Clay (1999), Narousa (2002), Al Farouk (2007) and Quantum Dude (2009).
The last horse to win the Nuggets twice was Frontline in 1983 and 1984.
Al Farouk and Borninthestates preceded their wins with success in the Waikouaiti Cup.
Peyow Peyow, winner of the Waikouaiti Cup last Saturday, is in the field tomorrow.
