...and why was Tszyu past his prime?? becuase he lost??

Didn't seem past his prime when he blew away (the then number 1 and favourite) Sharmba Mitchell inside 3 rounds.
Not much happend between the 2 fights to make him past his prime. He had had less fights than Hatton and had not been any wars to make him past his prime after 30 odd fights.

Was he past his prime against Philips, coz he was a sht load better against Hatton!!