Ajax is hiring “overperformer” Maurice Steijn as its new coach to replace John Heitinga, whose contract was not extended after the Amsterdam club finished a disappointing third in the Dutch Eredivisie. The club said Wednesday the 49-year-old Steijn will sign a three-year deal to join from Sparta Rotterdam, which he led to sixth place in the Eredivisie this season after rescuing it from relegation trouble a season earlier. Financial details of the deal were not disclosed. Steijn said he was a little surprised at getting the offer from the biggest club in Dutch soccer.