Was he injured or ill? If the latter then it's kind of understandable, sometimes you aren't sure how you'll be till you actually get out there and need to give a full effort, and if you can scrape through you can be feeling better by your next match.
Disappointing though =(
Someone said in this thread "abdominal injury", i don't buy it, this isn't the kind of injury that pop out like that out of nowhere.
Joke of a result, let a lucky loser play.