First play, TKO in the third.
Second, KO in the 6th
Third, KO on the first round.
Here's the key:
The upper cut does a lot of damage, but for the amount of energy that it takes, it isn't worth it.
You can get more punches in if you work with left + right combos (alternating?) before running out of energy completely than if you use any uppercuts.
If you use left + right combo/alternate you can take him down completely the first time before you run out of energy, most of the time.
Uppercuts aren't worth their cost.