Heart of Midlothian will be without the services of Calem Nieuwenhof for "a bit longer" after having his hamstring re-scanned.

The Australian midfielder returned to training during the international break to build back up after suffering an injury during the win over Celtic in March. He had hoped to return for the St Mirren clash earlier this month but the 23-year-old has now missed the last five games and will sit out the Rangers clash on Sunday.

READ MORE: New year, new Nieuwenhof: The inside track on midfielder's Hearts renaissance

"Much the same as it was," Naismith said about the injury situation. "Calem is still out. He is probably going to be out for a wee bit longer than expected. Boycie, Halkett and Haring are still out, everybody else is fit to play.

"Calem did come back into training but at a limited level. Pushing on became an issue so we've had it re-scanned. It's part of his tendon rather than just a soft tissue or a muscle injury. It's going to be a bit longer."

It is now a case of wait-and-see for Hearts over Nieuwenhof with no date put on his return.

"There is no timeline at the moment," Naismith admitted. "That's probably the one negative."

Nieuwenhof had been the team's most consistent performer since the beginning of the year and had won the club's Player of the Month award for February.

He spoke to Hearts Standard last month about his time at the club so far.