?Spain's Andres Iniesta (R) fights for the ball with Poland's Dariusz Dudka (L) and Jakub Blaszczykowski during a friendly soccer match in Murcia June 8, 2010. [Xinhua/Reuters Photo]

Spain midfielder Andres Iniesta looks most likely to miss his side's opening World Cup match after Wednesday's test confirmed a muscle problem on his right hamstring.

Iniesta was forced out of his side's 6-0 win over Poland on Tuesday night before half time. The Barcelona player had been instrumental in setting up Spain's two early goals before complaining of a hamstring problem.

He was substituted by Pedro Rodriguez five minutes before half time and after the game coach Vicente del Bosque confirmed the substitution had been a precautionary measure, but that the player would have to go medical exam.

Those tests have ruled out another tear in a muscle that has given Iniesta problems over the last 12 months, but show he is suffering from an edema, which usually require three or four days complete rest followed by three or four days more rehabilitation before a player can return to action.

Given Iniesta's recent injury history, which has seen him suffer three injuries in his right hamstring in the last year, the talented playmaker is likely to be ruled out of Spain's first group match against Switzerland on June 16.

"I am optimistic, because I knew it was nothing too serious. I have had worse injuries and now I can enjoy my day off before we travel to South Africa," said Iniesta.

Pedro could take his place in the starting 11, but Fernando Torres will also be pushing for a place in Spain's starting line up after confirming his recovery from a knee operation with a goal on Tuesday night.