“But it is worth looking into and I will be saying to them again, ‘do you think the boot could have had anything to do with it’?”

I see nothing wrong with that question. I don’t believe that Sir Alex was pointing out a deficiency specifically in Nike boots; I believe that he might have been suggesting the boots preferred by today’s players might sacrifice protection for increased speed.

As the article indicated, broken metatarsal injuries are common, unrelated to the brand of boot.

Should the issue be examined? Of course.