Rangers striker Steven Naismith has been warned he may not play again this season after a medical specialist assessed his knee injury.The 21-year-old former Kilmarnock player was forced out of Sunday's Scottish Cup semi-final in the early stages, shortly after a challenge from St Johnstone's Martin Hardie.

Naismith's injury will be assessed midway through next month, when he will learn if there is any possibility of him returning in time for the crucial final games.

There could be a chance of Naismith being available in time for the Scottish Cup final against Queen of the South on May 24.

Naismith's team-mates Allan McGregor and Chris Burke had their ankle injuries assessed today but timescales have not been set for their returns to action.

They both risk missing a large chunk of the remainder of the season.

The injuries to Naismith, goalkeeper McGregor and winger Burke have come at the crucial stage of Rangers' season, as they look to add the UEFA Cup, Scottish Premier League and Scottish Cup trophies to their CIS Insurance Cup triumph.

Midfielder Lee McCulloch could also miss the remainder of the season with the broken foot he sustained against Celtic last Wednesday, in the same game as McGregor had to hobble off with his ankle problem.

Naismith and Burke were forced out of the St Johnstone game in the opening quarter of the game, and the newly-injured quartet have joined Charlie Adam and DaMarcus Beasley on the sidelines.

Burke's injury is the least serious and likely to be the quickest to heal, and he could be available if Rangers reach the UEFA Cup final.

With two days remaining until the semi-final against Fiorentina, manager Walter Smith must cope without the injured six players and banned captain Barry Ferguson and Kevin Thomson.

He must find a midfield to face the Italians at Ibrox, and is expected to field five players across the middle, who could be Steven Whittaker, Steven Davis, Brahim Hemdani, Christian Dailly and Thomas Buffel.

Nacho Novo could also be a contender for a wide midfield role if Smith decides he needs some pace and attacking flair.

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