1. Katie Ledecky (United States, multiple freestyle swimming distances)
Ledecky announced herself to the world by crushing the field to win Olympic gold in the 800m freestyle in London four years ago. She's now the most dominant swimmer in the world. Three of her 11 world records came at the world champs in Kazan last year. She's the first swimmer to have won the 200m, 400m, 800m and 1500m at a major meet and has nine gold medals at the past two world championships. Simply the best. New Zealand's best, Lauren Boyle, should be on the starting blocks in the 400m and 800m finals alongside Ledecky, and is solid medal chance. Ledecky is 19 and a freak. Don't miss her.
2. Simone Biles (US, gymnastics)
The 19-year-old from Ohio is poised to be the star turn at one of the most eagerly anticipated events on the Games programme. She is the first woman to win three successive world allround championships, is the most decorated American woman gymnast, with 14 world champs medals, 10 of them gold (another record) and is the first African-American to be world allround winner.
Real star quality, and she's made the cover of Sports Illustrated in the leadup to Rio. She has a tumbling trick named after her, The Biles, a double back layout with half twist, and serious height. Check it out.
3. David Rudisha (Kenya, 800m)
Rudisha won Olympic gold in London four years ago in a still-world record 1min 40.91, but was surprisingly beaten into silver at the Commonwealth Games in Glasgow two years ago by Botswana's Nijel Amos by .30s. The 27-year-old has been battling to find his best form but managed a season best 1:43.35 in Hungary a week ago. He's officially ranked second in the world, but he's the man, a silky sight in full flow.
4. Wayde van Niekerk (South Africa, 400m)
The 24-year-old from Cape Town produced the fourth fastest alltime performance in winning the world champs crown in Beijing last year, in 43.48s. Van Niekerk's the first runner to break 10s for 100m, 20s for 200m and 44s for 400m. Watch for 2013 world champion American LaShawn Merritt and Grenada's Kirani James, the minor placegetters in Beijing, to provide a fabulous duel.
5. Michael Jung (Germany, eventing)
Although not if New Zealand have a say in it. Jung, 34 next weekend, is a master horseman who won gold medals in both the individual and team disciplines at the London Olympics four years ago. When he won the individual crown he became the first rider to hold the Olympic, world and European titles at the same time, all won on his champion horse La Biosthetique Sam. He has six four star victories and will arrive in Rio the rider to beat. Mark Todd was Eventing rider of the 20th century, but right now Jung is as good as it gets in eventing.