The Manchester United loanee collected the trophy for December after helping push the Black Cats into the promotion shake-up with a string of outstanding displays.
He scored three times in last month's fixtures for Tony Mowbray's men, against Millwall, West Brom and Wigan Athletic.
Those strikes took the 20-year-old's tally to six for the campaign but his all-round approach play has also impressed and, more recently, he assisted the dramatic late winner for Luke O'Nien in the Emirates FA Cup third-round tie at Shrewsbury Town.
When asked for his highlight so far this campaign, he told the PFA: "I don't have a favourite moment, maybe I'll wait until the end of the season to give you that answer.