Clowney definitely WAS an injury risk. His entire last season in college, he was dealing with a knee injury, which I later found out was a medial meniscus of his right knee. Microfracture surgery was already being considered. However, this would have severely affected his expected high Draft status. At the same time, throughout his last college season, he was dealing with a significant "sports hernia" (core injury). In addition, he was found to have painful bone spurs in his foot that season, as well as a concussion.
Clowney was to have surgery to remove the bone spurs, but he opted not to. After he was drafted, the Texans medical staff finally in June decided that he required repair of his "sports hernia." At the time, he was known to have weakness of both sides, but due to a potentially longer recovery (and not being ready to play at the beginning of the regular season), it was decided to treat the contralateral side conservatively. After that, his history of knee injuries/surgeries is well known.
Whether the grass pallet seam helped trigger or even contributed to the need for his knee surgery or not can be debated. What can't be debated is that Clowney was a very high risk for his subsequent knee history coming out of college.
A college history of previous meniscus damage, bone spurs known to cause core problems and compensatory knee injuries, "sports hernia(s)" causing core instability with high risk for compensatory lower extremity injuries, and concussions well-known to be associated with high risk of subsequent lower extremity injuries.
The signs were already there for anyone, especially trained medical staff, paying attention.