MADRID — Rafael Nadal announced Thursday he will retire from tennis at age 38 following next month’s Davis Cup finals. Nadal won 22 Grand Slam singles titles during an unprecedented era he shared with his rivals in the so-called Big Three, Roger Federer and Novak Djokovic. [time-brightcove not-tgx=”true”] “Really, everything I have experienced has been a dream come true,” Nadal said in an announcement on social media.