Waghorn has been an instrumental figure for Gers this season, topping the club’s scoring charts as the Glasgow side sealed a return to the Scottish Premiership by winning the Championship.
However, the 26-year-old has barely featured over the past two months following a knee injury sustained in the Scottish Cup encounter with Kilmarnock, making him a doubt for the final.
With Waghorn facing a race against time in order to be fit to face Hibs, Milner has told reporters that his strike partner is on course for a full recovery as he featured in the recent friendly against Tottenham Hotspur.
"He has looked decent. He has been training for a while now. The 75 or 80 minutes that he got the other will have been good for him. Okay, it was a closed doors game, but there was a real intensity about the performance,” Miller told Herald Scotland.
Waghorn has netted 28 times for the Ibrox club this season, illustrating his importance to the team.
With Rangers looking to seal a treble when they meet Hibs in the final of the Scottish Cup, they will be hopeful of lining up with their strongest team available as the Edinburgh side will pose a difficult proposition.
Waghorn played for an hour in the recent 2-2 draw with St. Mirren, and his appearance against a Spurs XI in a competitive recent friendly will have enhanced his fitness further ahead of the final.