Mick McCarthy says he's at a loss to explain Alex Smithies' withdrawl during the 2-0 Severnside Derby win over Bristol City on Saturday.
Smithies sparked concern after just nine minutes, signalling for medical attention after slumping down beside the post.
The delay saw eight minutes of added time in the first half, with Smithies brought off on a stretcher before being replaced by Dillon Phillips.
And, speaking after the victory, McCarthy's first as Cardiff boss, it seems the cause of his illness is still a mystery.
"I've just been in to see him with the physio," the Cardiff boss said. "He's sat up and we don't know if he's had an allergy or something.
"I don't think so. They all had the pre-match meal and it was all the same stuff. I doubt that very much.
"He looked very ill at the time. He was brought off on a stretcher. That looked worrying. But I've been to see him and he seems OK. So I've no idea. But he was quite ill at the time."
Asked specifically what was wrong with the former Queens Park Rangers keeper, McCarthy continued: "I've told you. I don't know.
"He was sick."
Losing their number one could well have upset what was otherwise a bright start from the Bluebirds, but McCarthy said he was pleased by the character shown by his team on what eventually proved a reasonably comfortable afternoon.
"We had to work damned hard to get that," he added. "I thought we started really well. Of course when you're two up, it always gives you a chance, but the lads have worked exceptionally hard."
Cardiff will now turn their attention to Rotherham United on Tuesday night, and it remains to be seen whether Smithies will be fit for it.
There are still doubts too over Jonny Williams, who sat out the trip across the Severn with a knock in training.
"Typical Jonny," McCarthy said.
"He gets clattered in training. It was a bang on the back of his knee. I don't think it'll be long.
"Maybe next week."
