It was bad enough that the Chicago Blackhawks were without Jonathan Toews, their center and team captain, for the entire 2021 NHL season. What was worse, however, was that very few knew exactly what was wrong with him while he was out.

Toews, a Blackhawk since 2007 and a three-time Stanley Cup Champion, sat out the entire season with an undefined medical issue, which he described in December only as symptoms which left him "drained and lethargic." Toews' extended absence, combined with the ambiguity surrounding his condition, generated a great deal of concern for the Blackhawks' captain.

But on Wednesday, Toews shared more about what his illness had been as he made his return to the Blackhawks' team facility and suited up once again for some light practice.

Here's what he said, via a video posted on his Twitter page:

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"I just think there's a lot of things that just kind of piled up where my body just fell apart. So what they're calling it was chronic immune response syndrome, where I just couldn't quite recover and my immune system was reacting to everything that I did," Toews explained. "Any kind of stress, anything that I would do throughout the day, there was always kind of that stress response. So it took some time, and that was the frustrating part was not really knowing when or how we were gonna get over the hump.

"But thankfully I've got a great support team of people that helped me through it, and learned a lot about just the stress I've put on my body over the years."

In sharing how he appreciated the support he received during his absence, Toews expressed some contrition over the level of concern there was for him. 

"A lot of people were worried, and [I] definitely felt bad to a certain degree that people were that worried that they thought it was really serious," Toews said. "But in the back of my mind I knew I'd get through. It was just a matter of time."

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While Toews' video presented a promising step in the right direction for him, he did not disclose any information concerning a timetable for his return to hockey.