Why didn't Phelps take part at all the swimming categories (like 100m Backstroke, 50 freestyle or 800 m) ?

Question

Do you think he stood any chances ?

Answer 1

just too many races, he would burn he self out!

Answer 2

He is not a good enough starter to compete in the 50 m. He is also not a distance swimmer. His specialty is his turn off the wall. So that helps him in distances like 100m, 200m.

Further, the free style and butterfly are his strong strokes. He can also do the backstroke and breaststroke, but not good enough to compete with specialists in those strokes. He is good enough though to win the individual medleys.