Hazard is again struggling with injury in El Clasico week.
"Madrid tends to be very patient with these types of players," Morientes said.
"We know Hazard is very good, but there will probably be a time when Real Madrid will have to make a decision.
"This year is a decisive year, it's crucial for him and he will have to demonstrate what he's got."
He added: "They have waited two years for him to reach his top level. This year was a year in which the club, the fans and his team-mates expected the best Hazard but he hasn't started in the best way possible.
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