Southern Miss (24-6, 11-4 Conference USA), which is receiving votes in the Associated Press poll, led for the entire game, but struggled to put the Mustangs away. Watson scored 13 of his 18 in the second half as the Golden Eagles pulled away in the final minutes.
Southern Miss shot 52.2 percent (24-of-46) from the field and enjoyed a huge 37-19 advantage on the glass. The Golden Eagles stayed one game behind Memphis for the C-USA lead.
SMU (12-18, 3-12) was led by Robert Nyakundi's 18 points while Jeremiah Samarrippas added 13. Nyakundi hit three 3-pointers in the second half to keep the Mustangs in the game. Rodney Clinkscales also scored 10.
The Mustangs close out the regular season this Saturday, Mar. 3 when they host UTEP at Moody Coliseum.