Al Faiha took the lead in the 11th minute through Ronnie Fernandez.
Al Nassr were reduced to 10-men when Australia goalkeeper Brad Jones was sent off in the 65th minute.
The visitors however rallied back with a hat-trick from former Morocco international forward, Abderrazak Hamdallah with Musa setting him up twice.
Sultan Al Ghanam got the other goal for Al Nassr.
Musa, who has struggled with injuries this season has made eight league appearances for Al Nassr and is yet to open his goal account in the current the campaign.
Al Nassr occupy top spot in the league on 29 points from 13 games.