The Canada international started all three matches in the division as Barry Lewtas’ team took six points, including a 1-0 win over Everton and a 5-3 victory at Manchester United.
Millar’s impressive form earned him a nomination for the monthly accolade, with the candidates decided by the Premier League Football Development Panel after PL2 coaches selected the best performance by an opposition player in each fixture.
The Reds man is up against Scott Banks (Crystal Palace), Josh Bowler (Everton), Sam Greenwood (Leeds United), Mitchell Clark (Leicester City), James McAtee (Manchester City) and Brooklyn Lyons-Foster (Tottenham Hotspur).