From the PG:
"Steelers receiver Sammie Coates said via his Twitter account Monday night that he had surgery on his groin. Coates did not specify when the surgery took place, but he did not let on during the season that he was dealing with a lower body injury."
http://www.post-gazette.com/sports/Steelers-Blog/2017/02/13/Sammie-Coates-reveals-on-Twitter-he-had-groin-surgery/stories/201702130182
"Steelers receiver Sammie Coates said via his Twitter account Monday night that he had surgery on his groin. Coates did not specify when the surgery took place, but he did not let on during the season that he was dealing with a lower body injury."
http://www.post-gazette.com/sports/Steelers-Blog/2017/02/13/Sammie-Coates-reveals-on-Twitter-he-had-groin-surgery/stories/201702130182