With the Dragons dominating the Rabbitohs everywhere except the scoreboard in the first half, McGregor interchanged James Graham, Paul Vaughan and Jack de Belin simultaneously in the 27th minute.
Leeson Ah Mau, Jeremy Latimore and utility Kurt Mann, who played lock, were their replacements.
The starting trio were re-introduced gradually before the midway point of the second half to help the Dragons late in the match when the possession stakes inevitably shifted back towards their opponents.