De Jong suffers hamstring tear
The Netherlands midfielder was withdrawn after eight minutes of the goalless stalemate and replaced by Kolbeinn Sigthorrsson.
De Jong is now faced with a lay-off that will ensure he misses the crunch clash with second-placed FC Twente, who are now seven points behind the Amsterdam club in the race for the Eredivisie title, a week on Sunday.
Ajax revealed that his injury will be re-examined in two weeks as he also faces up to the disappointment of missing the KNVB Cup semi-final against AZ Alkmaar..
"The midfielder was examined on Monday at the hospital," read a statement on the club's official website.
"This study found a tear in the right hamstring, which means De Jong will not be used in the coming weeks."
De Jong, who was linked with a move away from the club in the close-season, has scored seven league goals in 18 appearances this term.