Monaco, winner of last week’s tournament in Houston, suffered an ankle injury during a rally in the third set as he stretched for the ball. Although he received immediate medical treatment, the injury proved to be too serious for him to continue playing.
Haase will face Italy’s Fabio Fognini next, who beat Michael Llodra of France 7-5 6-3.
Pablo Andujar, the winner of last week’s clay court tournament in Casablanca, moved into the second round by defeating the Argentine qualifier Federico DelBonis in three sets 3-6 6-4 6-2.
Andujar’s next opponent will be the Swiss Stanislas Wawrinka, who dismissed the 10th seed Feliciano Lopez of Spain 6-1 6-4.