A typically cagey north African showdown produced barely any scoring chances for a large crowd at the 80,000-seat Stade du 5 Juillet.
The match did nothing to enhance the reputation of the elite African club competition with an 80th-minute incident demonstrating the poverty of the football.
The Algerian outfit monopolised possession throughout, but were clueless when it came to creating final-third space.
When Wydad substitute Abdeladim Khadrouf was pushed in the back with only a few minutes remaining, he fell to the ground clutching his face and triggering a long delay.
Carried off on a stretcher, the Moroccan immediately got up and ran back on the field.
USMA forced two free-kicks and a corner in stoppage time without threatening to end the dreary deadlock.
Former champions Wydad host the return match against 2015 runners-up USMA during the weekend of October 20-22.
Etoile Sahel of Tunisia have home advantage over record eight-time champions Al Ahly of Egypt in Mediterranean resort Sousse
Sunday in the other first leg.
The four title contenders are chasing a record $2.5 million (2.1 euros) first prize.