There's no way Sasuke would win at the Chuunin Exams at that point. Sasuke had Lion Combo, Great Fireball, Chidori, pretty smooth taijutsu skills, and two-tomoe Sharingan. Neji had Jyuuken, 8-Trigram Rotation, 64-palm attack, and his Byakugan watching him do everything.
Every taijutsu battle would be very stressful for Sasuke, as any blow delivered to him would damage his chakra network. With his chakra, he wouldn't be able to spam Great Fireball every time, and even this is under scrutiny as we don't know exactly how 8-Trigram Rotation would handle it.
Being under the aid of his Curse Mark is out of the question, as he himself wanted to suppress it at any point that it would awaken, and the Jounin were keeping an eye on him--any time that the Curse Mark would awaken would mean the match would end abruptly.
His two-tomoe Sharingan may be able to see Neji's 64-palm attack, but it does not mean he can dodge it. One devastating blow for Sasuke would spell KO for his chakra network, and his inability to continue. Naruto won his fight against Neji, because he circumvented the loss of his chakra network with Kyubi chakra and defeated Neji while he was tired. Sasuke doesn't have a second chakra source.