The forward limped out of their 1-1 draw on Tuesday evening.
The forward could only manage 25 minutes in the game before he had to leave with a hamstring injury.
It is not the first time he has picked up such an injury this season, having missed three months of the season with a hamstring injury earlier in the campaign.
Rangers will now have to wait to see the extent of this latest set back, and Hasselbaink has confirmed that things do not look good for him.
“He’s got a hamstring problem and I hope it won’t be too bad, but it doesn’t look good,” West London Sport reports him saying
“It’s something we’ll have to assess in the next 48 hours. Jamie is someone who would never want to come off. He will play through pain and if he has to come off it’s normally something not good.”
Mackie’s injury encapsulated a disappointing evening all round for Hasselbaink’s side as they struggled to create chances throughout.
They failed to test debutant goalkeeper Bailey Peacock-Farrell, who was making his senior debut in the game.
Instead they required a late penalty from Tjaronn Chery, his tenth goal of the season and sixth in his last nine matches, after Chris Wood had fired Leeds ahead on the hour mark to earn share of the points.
The result leaves them 11th in the table with 52 points to their name with six games remaining this season.