Here's a video of the race in which Yohan Blake severely injured his hamstring:
https://www.youtube.com/watch?v=zZjue7uX4jo
And he's a link to the LRC article posted yesterday, 22 June 2016, "The Rebirth Of Yohan Blake:"
http://www.letsrun.com/news/2016/06/rebirth-yohan-blake/
Blake failed a test some years ago as he tested positive for a stimulant. Here's a relevant passage from the Wikipedia entry for Blake:
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Drug ban
Prior to the 2009 World Championships, Blake (along with Marvin Anderson and Sheri-Ann Brooks) tested positive for the stimulant 4-methyl-2-hexanamine.[19][20] A disciplinary panel organised by the Jamaica Anti-Doping Commission (JADCO) cleared him of a doping infraction on the grounds that the drug was not on the World Anti-Doping Agency's banned list. However, JADCO appealed their own panel's ruling, stating that the athlete should be disciplined as the drug was similar in structure to the banned substance tuaminoheptane.[21] As the panel would resolve the issue after the World Championships, the Jamaica Amateur Athletic Association took the precaution of withdrawing Blake from the relay race.[22] The appeals tribunal decided that a ban would be appropriate, and Blake and the three other sprinters each received a three-month ban from competition.[23]
from
https://en.wikipedia.org/wiki/Yohan_Blake
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Might that drug have been a risk factor for the injury he suffered?