For the 31-year-old, one of the heroes of last season’s promotion-winning team but yet to appear in the Championship this season after the arrival of former England goalkeeper Chris Kirkland, was struck down with pneumonia and spent three weeks on the sidelines.
His condition was so serious the bed-ridden footballer struggled to even speak at the peak of the illness.
So a return to action in a behind-closed-doors friendly against Huddersfield Town on Tuesday was a timely boost for the former Derby County goalkeeper.
“I had a headache virus for 10 days, that turned into a chest infection, and that turned into pneumonia,” he said.
“I couldn’t believe it. It’s hard to breathe. You can have a conversation and you’re out of breath.
“I had it in my left lung; the doctor said it was the worst chest he’d heard in years. I was suffering – I had to stay in bed and rest.
“I’m quite fit, supple and strong; I always have been. That helped me through it.
“Now I’m available to contribute to Sheffield Wednesday again. It was good to have a run-out in the game.
“There’s nothing worse than being in bed when the results are coming in, and you can’t do anything to help.
“The physios have been first class, and the gaffer has been brilliant. He told me to take as much time as I needed.
“It’s good when you’ve got people like that behind you and you’re not made to feel uncomfortable.”
Bywater’s return gives manager Dave Jones options now for the goalkeeper’s jersey, although he accepts he faces a fight to oust Kirkland, who has impressed since his summer switch from Wigan.
“I’ll keep going. I’m working with Chris and we get on well,” said former England Under-21 star Bywater.
“It’s a team effort. I’m happy to back whoever’s playing and I’m ready if called upon. That’s the way of this job.
“The manager looks after me, treats me like a man and a professional, and I’ve got a lot of respect for him for that.”
The Owls have been allocated 5,700 tickets for the South Yorkshire derby with Barnsley at Oakwell on December 15.
n Blackburn Rovers’ Bradley Orr has joined Championship rivals Ipswich Town on loan.
The 30-year-old has played 12 times for Rovers this season but has not featured in any of their three games under new manager Henning Berg.
Orr will stay at Portman Road until the end of January.