Who is the biggest what-if in men's tennis history?

Injuries, walk-aways and talent that never quite converted. The careers that leave you wondering.

1. 1
   Bjorn Borg

   Won eleven majors and walked away from the sport at 26.
   1000pts
2. 2
   Juan Martin del Potro

   Won the US Open at 20, then lost years to wrist and knee surgery.
   512pts
3. 3
   Goran Ivanisevic

   Lost three Wimbledon finals before finally winning as a wildcard.
   512pts
4. 4
   Milos Raonic

   One of the great serves of his generation and one major final.
   444pts
5. 5
   Richard Krajicek

   Won Wimbledon in 1996 and lost years to knee and elbow trouble.
   444pts
6. 6
   Gustavo Kuerten

   Three French Opens and a world No. 1 ranking, ended early by a hip injury.
   363pts
7. 7
   Marat Safin

   Beat Sampras and Federer in major finals, and won only two titles.
   363pts
8. 8
   Nick Kyrgios

   Beat every member of the Big Three and reached one major final.
   363pts
9. 9
   Andre Agassi

   Won five of his eight majors after turning 28, having fallen to No. 141 at 27.
   363pts
10. 10
    Ernests Gulbis

    A French Open semi-finalist whose talent never settled into a career.
    266pts
11. 11
    Tommy Haas

    Reached No. 2 in the world and spent much of his prime injured.
    148pts
12. 12
    Robin Soderling

    The only man to beat Nadal at the French Open before illness ended his career.
    148pts