What to watch: Katie Ledecky gets her last chance at setting a world record at Trials with the 800 free final. In prelims, she blazed a long-course Nationals record time of 8 minutes, 10.91 seconds. The time smashed Janet Evans’ 1988 record of 8:17.12. “She’s incredible,” the former El Dorado star said of Ledecky, who challenged her world record in the 400 free. Michael Phelps and Tom Shields could renew their rivalry in the men’s 100 butterfly final. It also could be Phelps’ final race on U.S. soil since he has vowed to retire after the Olympics. Defending Olympic champion Missy Franklin could build momentum for Rio with a strong effort in the women’s 200 backstroke final.