Mladenovic suffered with injury in his short time at Rangers

The 29-year-old Serbian international moved to Spain on loan in February and Sociedad had the option to retain his services for a fee of around �600,000.

But he didn't do enough in his 12 appearances to earn a permanent move.

Mladenovic joined Rangers from Red Star Belgrade for �1.2m last summer but failed to impress after picking up an injury early in the season.

He made just nine appearances in six months at Ibrox and the January arrivals of Barry Ferguson and Thomas Buffel pushed him further down the pecking order.

Mladenovic signed a four-year deal with the Scottish champions but Rangers are expected to let him leave on a cut-price deal.

The player had been speaking to clubs in Germany and Russia before joining Sociedad.