He recovered in time for the Olympic trials but despite that, he was told a week ago that he would only be a reserve for the London Games.
"To just miss out, it sucked all the life and energy out of me. I just moped around the house for the rest of the day.
"But I am reserve and I've got to keep training. I don't wish it on anybody, but if anyone does get injured I'll get the nod, so I have to make sure I'm fit and ready," he said.
"I have appealed it but unfortunately it got rejected and I'm not going to take it any higher or further."
He added: "At the  British Championships I got two golds and three bronzes, I got two silvers at grands prix this year and personally, I thought that would have been enough to make the team, but obviously in other people's eyes it wasn't."
The GB men's team will be led by Keatings' club-mate Louis Smith, a bronze medallist at Beijing in 2008, while Dan Purvis, Kristian Thomas, Max Whitlock and Sam Oldham have also been included.
"The depth in the British gymnastics squad is unbelievable compared to four years ago when me and Daniel were pretty much the only people even getting the qualifying scores to go to the Olympics," Smith, 23, told BBC Radio Cambridgeshire.
"This time around you had about eight or nine people fighting for just five places and unfortunately Daniel Keatings, my team-mate who I've trained with for about 12-13 years, didn't make the team.
"It's sad I can't be here with him, but then you have to look at the positives and say that's how far and how deep the British men's team goes."
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