Hazard was substituted after 28 minutes in Madrid’s 2-1 La Liga defeat to Alaves on Saturday.
Initial tests carried out on Sunday were inconclusive, but a scan on Monday morning confirmed that the Belgium international had damaged his thigh.
“Following tests carried out today on our player, Eden Hazard, by Real Madrid Medical Services, he has been diagnosed with an injury in the rectus femoris muscle of his right leg,” the club said in a statement. “His recovery will continue to be assessed.”
Sources told ESPN that Hazard is expected to be out for at least the next three weeks.
That would see the forward miss tough La Liga fixtures with top-four contenders Sevilla on Dec. 5, and the derby with Atletico on Dec. 12, followed by games with Athletic Bilbao and Eibar. Diego Simeone’s Atletico are six points ahead of Madrid in the table, with a game in hand.
Ahead of Tuesday’s game they are second in the group, a point behind Monchengladbach, and three ahead of Shakhtar.
Hazard had started three games in a week for Real Madrid, and there were positive signs that he was finally starting to find some form, scoring from the penalty spot in a 2-0 win over Inter Milan last week.
He had only just returned to the team after testing positive for the coronavirus, and before that was absent for a month with another muscular problem.
Hazard’s first season at the Bernabeu was, by his own admission, a huge disappointment, with two ankle fractures limiting him to 16 La Liga appearances and just one goal.