The 26-year-old has featured in five games in all competitions for Sunderland this season, and will travel to face Queens Park Rangers in the League Cup on Wednesday.
"He had the statutory checks with the cardiologists," Moyes told reporters on Tuesday. "The Football Association panel advised us really late that he should not play until further tests had taken place.
"I can categorically say that all conspiracy theories are incorrect. It was completely out of our control. We had to make the correct decision for the player and for the football club."
Moyes said striker Jermain Defoe will not feature against QPR after picking up a knock.
"We need to make sure he's fit for the weekend. Some players need game time but some need a rest, so we will take a good team down but we will make a couple of changes," Moyes added.
Sunderland face Crystal Palace in their next league fixture on Saturday.
(Reporting by Nivedita Shankar in Bengaluru; editing by Sudipto Ganguly)
