The Shrewsbury manager spent a total of 49 days in Bristol Royal Infirmary Hospital after initially being admitted to intensive care in January.
Complications in his recovery, including Covid-pneumonia, would also see him return to hospital for a second period.
During his four-month absence, Cotterill missed 24 games, with his assistant Aaron Wilbraham taking over the reins.
However, the 56-year-old oversaw Shrewsbury’s return to pre-season training on July 1.
And a visibly emotional Cotterill has issued a video thanking people for the support he received through such a difficult time.
Cotterill, who spent 15 months as Pompey manager before leaving in October 2011, told Shrewsbury’s official club website: "First and foremost, if I do get emotional through any of this I apologise because there will be moments which will bring a fair bit back to me.
‘Apologies to all at Shrewsbury Town. I sort of feel I let you down last year.
‘The chairman, board of directors, staff, players and supporters really. I wanted to get back before the end of the season and managed to get back for the last three games, I'm not sure that was a good idea really. I wasn't anywhere near ready and my recovery time after watching a game was quite long, quite lengthy.
‘Ever since the season finished, I've been in the gym every week to try to get myself fit to come back on July 1, just to be around the players and the new players we signed.
‘For those people out there that have suffered from Covid – we will do some 'Covid interviews' through pre-season, that will be interesting for a few people, certainly those that have suffered with Covid will probably be aware of the depths you go to.
‘The next bit is thank yous, the chairman, to the CEO, the board, staff, players, the supporters, have been incredible to me really.
‘Special mentions have to go to Aaron Wilbraham and David Longwell who carried the brunt of it, certainly Aaron, and all the other staff for keeping it going in my absence.
‘I think the players last season, they are not here anymore, should never ever be forgotten for what they did.
‘With the start to the season, the change in manager, and then an assistant and a first-team coach running it from there. I don't think any of those players, even though they've left the football club, should ever be forgotten.
‘While there wasn't any major achievement, any promotions, any cups won, there was an incredible amount of effort put into it.
‘Also thank you to my previous clubs I’ve managed, for the goodwill messages, whether through email, social media, somewhat 2,000 texts in hospital, it took weeks to answer them, which was incredible and quite emotional.
‘A huge thank you to our own supporters for the get well cards, messages, the banner behind the dugout, the money raised for the NHS.
‘I remember when I saw the banner for the first time, that did give me a lump in my throat and still does.
‘Football can be a tough place and it has been over the years – and really tough – but what I will say is it’s a very strong family in adversity and I definitely benefited from that. So thank you.
‘I have never mentioned this before, but privately over the years there have been lots of people, lots of donations that I have made which has helped disadvantaged people, children, I never wanted anything back, never wanted any publicity for any of it, or wanted any thanks.
‘But the love and kindness which has been shown to me over this tough period is overwhelming. So I just want to thank everybody.’
A message from the Editor, Mark Waldron
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