The duo came through the ranks together at Aston Villa.
Aston Villa were beaten 2-0 by Preston North End on Saturday afternoon.
Preston North End are due to take on Aston Villa at the weekend.
Grealish signed a new four-year deal at Villa Park on Wednesday.
Queens Park Rangers fans made their feelings clear on Twitter after the club's defeat to Preston North End in the Sky Bet Championship
Preston North End lost 1-0 at home to Derby County in tonight's EFL Championship encounter.
Callum Robinson has left Aston Villa for Preston North End in the summer transfer window.
Jack Grealish has wished his former Aston Villa teammate Callum Robinson luck following the completion of his move to Preston North End.
The 21-year-old striker has joined Preston North End permanently after previously enjoying three loan spells at Deepdale.
Ian Wright also sent a message to the youngster after he completed a move to Preston North End.