It will take a long time to drain Sentry, since he has the power of a million exploding suns. By the time time he realizes this, Triumph will be eaten by the Sentry's thought manifestation, the Void, or Sentry will simply beat the holy hell out of him. Something Superman could not since he was being drained and stores solar energy in his cells where the Sentry has the power of a million Exploding Suns and can still fight on even if being drained.. He says so himself.
Superman helpless:
http://img.photobucket.com/albums/v345/sifu1/siphonenergy.jpg
Sentry saying he has the power of a million exploding suns...
http://img.photobucket.com/albums/v345/sifu1/sentry.jpg
Sentry wins. Cause whenever their's Sentry, there is the Void.
Sentry is a double edged blade.