Poland twice came from behind to salvage an unconvincing 2-2 home draw with Iceland on Tuesday and left their manager Paulo Sousa with plenty to ponder after their final dress rehearsal for the European Championship.
Iceland were pegged back early on and took the lead out of the blue when Gudmundsson tucked the ball away at the near post with a clever back-heel after Gudmundur Thorarinsson swung in a corner past a static Polish defence.
Zielinski equalised with a clinical finish before the break, sweeping the ball home from the edge of the six-yard box after a flowing move started by their record scorer Robert Lewandowski.
But more slack defending cost the Poles again as they failed to clear a Thorarinsson cross from the left and centre back Bjarnason blasted an unstoppable volley into the roof of the net from 12 metres.
With time running out for Poland, Swiderski levelled shortly after coming on for Lewandowski as he chested down a cross from the right and scrambled home a low shot from close range.