Basketball Hall of Famer Hakeem Olajuwon of the Houston Rockets is an observant Muslim; a Reddit post [0] says his game performance dropped a bit during Ramadan, but he still managed to lead the team to two consecutive NBA championships. (Apparently Ramadan never occurred during the playoffs during the years in question.)

[0] https://www.reddit.com/r/nba/comments/3yvhf2/hakeem_olajuwon...