City jetted out to North America earlier this month, but Onuoha was among a group of players left to train back home.
Onuoha along with the likes of Jo, Craig Bellamy, Wayne Bridge and Emmanuel Adebayor were all told by e-mail they were not travelling with the first-team squad, much to the defender's annoyance.
The stopper, who spent last season on loan with Sunderland, felt the club could have handled things much differently, although he is not dwelling on the matter.
The 24-year-old still has three years left to run of his City contract and he remains positive on his predicament and has not given up hope of coming back into favour under manager Roberto Mancini.
"I'd love to stay and fight, and until someone tells me to jog on then I'll keep trying," he told the Manchester Evening News.
"To be honest, we're just being professional at the moment. There's a lot of disappointment about what happened and how it happened.
"You could say that people make mistakes and the situation could have been dealt with a bit differently.
"But as far as the players are concerned, none of us are down in the dumps. We're just determined that we're going to give everything we can.
"At the end of the day, we might not be on tour but we've not been shown the door so we've got to keep going.
"We're still being paid by Manchester City. We're in pre-season so it's always going to be hard. But in any games you have, you should always try your best because you have to be ready for a big season.
"As far as I'm concerned, I'm going to keep going through pre-season. Nothing's changed on my side and it's the same with a few of the others too.
"I don't have a locker, I don't have a squad number now, but other than that, it's same as.
"It's a case of coming in during the week, training hard and getting ready for any games that we have. I think the first team are back in just over a week's time so things might be different then."