Toronto Raptors guard Terence Davis -- one of the best rookies in the NBA last season -- was arrested Tuesday after he allegedly socked his ex-GF in the face multiple times ... TMZ Sports has learned.
Law enforcement sources tell us Davis was staying with his ex-girlfriend at the Beekman Tower in Midtown Manhattan, N.Y. ... when the two got into an argument.
Unclear what prompted the dispute ... but our sources say things got out of hand quickly -- with Davis allegedly punching the woman in the face REPEATEDLY.
We're told the altercation escalated even further after Davis' ex-GF refused to stop filming the NBA player with her phone .