The Dutch striker was performing well at St James' Park and was close to scoring what would have been a sensational goal in the first half, when he was denied by Nick Pope's save.
However, after a sustained dribble in the Magpies' half, he pulled up sharply, clutching at his hamstring and it was clear he needed to instantly be replaced.
As he was helped off the field, Zirkzee was shown sympathy by a couple of Newcastle players, and he looked understandably upset as he left the field.
During his post-match interview with MUTV, Amorim admitted the picture does not look good for Joshua, with the problem coming at the worst possible time.