Michael Phelps has said that South African swimmer Chad le Clos will lead the sport in the future as he prepares to retire.
Phelps will race for the last time in Saturday's 4X100m medley relay final after winning 21 Olympic medals.
Le Clos has won two medals of his own at London 2012, notably beating Phelps to win gold in the 200m butterfly.
Phelps thinks that Le Clos will take some stopping over the next few years.
He told BBC Sport: "I'm leaving at a good time. The sport is going to be fun to watch, I'm excited to see it from the outside more than anything and see what these guys continue to do to change the sport.
"It's going to be fun to watch Chad and see what he does for the next four years. It's been very fun to race him a couple times and sort of get to know him."
Phelps claimed a record 17th gold medal on Friday in the 100m butterfly in the last individual swim of a glittering career.
