Novak Djokovic and Serena Williams will open Wimbledon, which begins Monday, as favorites to retain their singles titles, yet much has changed for both players since their triumphs last year.
Djokovic arrived the All England Club 12 months ago having a third French Open final defeat in four years. His hopes of completing a career Grand Slam were ended by an inspired Stan Wawrinka.
MORE: U.S. winners of Open Era | Recent Wimbledon champs
He hasn't lost a match in a major tournament since then. Having won at Roland Garros earlier this month, Djokovic holds all four major titles and is the first man to do so since Rod Laver in 1969.