Center back Isak Hien had already left the field - and subsequently the national team - at the end of the first half.
When Gudmundsson sat down and grabbed his leg, he likely had a few scares. In the 77th minute, he came off for Daniel Svensson.
"I immediately felt it was a blow. If it had been a twist, I probably wouldn't be standing here today," he said in the mixed zone.
Gudmundsson was excellent against Ukraine. But that's history. On Tuesday night, Sweden can secure a World Cup spot in the qualifying final against Poland.
The most important match of my career is tomorrow. That's when you have to go out and deliver.
Corrected: In a previous version, Sweden's opponent was incorrectly stated. The correct opponent is Ukraine.
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