It's a fairly common injury, it appears. I had a very similar sort of experience myself all the way back in my undergraduate days - one of my first days at university, actually. Heavy challenge came in while I was going down the touchline, and my ankle gave way under me. Same sort of reaction as your team-mate had - I was struggling to breathe for a bit, the pain was so intense and so sudden.
But, unlike Harry and any other reasonably sensible chap, I actually tried to go on playing when I felt a bit better. Big mistake - couldn't last more than five minutes, but the damage was done, because I could see and feel my foot visibly swelling up as I struggled back to my dorm. By the time I got back, it was massively bruised and swollen(size of a rugby ball, or so it seemed) and I couldn't do anything other than prop it up and wait for morning. When I finally got to the sports injury specialist at the uni gym, he told me bluntly that I'd turned a month-long rehab period into three months or more of close treatment.
Basically ended my outfield career, because by the time I got back the only spots open in the intramurals were for goalkeepers - so I signed up as one, discovered I was roughly decent at it and stayed a keeper from then onwards. Fortunately, I don't think that's a fate Harry will have to suffer - if his spell in goal against Asteras is any indicator.
Hopefully, it turns out to be just three weeks to a month and he'll be back fit and firing by the end of April.
