League One player of the year Bradley Dack scored twice as Blackburn came from behind to defeat Peterborough 3-1 at Ewood Park.After Charlie Mulgrew's own goal gave Posh a deserved lead, Dack nodded in a second-half equaliser before Danny Graham's close-range header completed the turnaround.Dack rounded off the win in injury time with his 18th goal of the season as Blackburn stretched their lead over third-placed Shrewsbury to eight points.The visitors bossed the first half and were denied close to the break by a wonderful David Raya save from George Cooper's pinpoint free-kick, but Mulgrew headed the resulting corner past his own goalkeeper in the 44th minute.Blackburn roared back after the break as Dack powered home a header in the 54th minute.And seven minutes from time, Dack's header thundered back off the crossbar and Graham nodded home the rebound.Graham returned the favour in injury time, slipping Dack in who emphatically slotted home, sending the home fans into raptures after securing a vital win.