Rock and Manassero are the only golfers competing on the King of Morocco's Royal Course in Agadir who can qualify for the Masters at Augusta National.
Rock lies 57th in the world rankings and Manassero 61st, and either must win to be inside the top 50 and gain direct entry into the year's opening major.
"Augusta and qualifying for the Masters is the reason why I played in Spain last week and I'm here this week in Morocco," Rock said.
"The only way I can now really get into the Masters is to win this week, and given how well I played in the Andalucia Open, I'm quietly confident of doing enough to get myself inside the top-50.
"I have left it a bit late to try and get myself into the Masters, but I'm sure I will be well inside the top 50 by the time the U.S. Open comes around (in June). But having to achieve that goal this week is going to be a bit hard, but at least it gives me something to focus on."
Rock dropped one place in the rankings in finishing tied for 17th in last week's Andalucia Open.
The 18-year-old Manassero picked up two places in finishing second to Frenchman Julien Quesne.
Quesne was also in Morocco after winning his maiden European Tour title.
"Everything has been great these last two days and I can't believe the amount of people who have congratulated me and that is very special," Quesne said.