If we are focusing on only Naruto and Sakura then I believe that Naruto beats her even without ninjutsu.
We are restricting the molding of chakra, so no punches have chakra enhancements, no movements have chakra enhancements, and everything is determined the same as our mundane fights.
With that said, Naruto definitely has reach and weight on Sakura. Because this is not a comparison of how much chakra was poured into a movement to enhance it, they probably move at similar speeds, and it would come down to personal fighting styles. Naruto is built to go head to head, blow for blow with his opponents. He rarely used kicks in his fighting style, so he is more of a rush down and out-punch fighter. He also boasts excellent stamina naturally and above average endurance (he fought with Sasuke to a standstill for most of a day without falling.)
Sakura is more of a counter fighter, and would allow Naruto to swing away at her until he throws too much of an easily read punch and she launches a counter to his chin. However, this would not happen easily because Naruto's reach is longer, and he has been shown to take hits and recover fairly quickly. All Naruto would have to do is keep up the offensive and chip away at Sakura's endurance/guard. If she backs into a corner it is over for her because he can, due to his stamina, continue his assault for a long time. Naruto is NOT a defensive fighter, and the only way to beat him is by overwhelming his offense. Unfortunately this is not something Sakura can do in a boxing ring.
What do you think?