Speaking to Sky Blue World, the keeper, who was player of the year in his first season at City said: "Initially my mindset is to get fit. Once that's been overcome I'll look forward.
"The manager is going to have to bring somebody in with Dimi out long term and me touch and go for the start of the season. "If it's Kasper I've got a fight on my hands, that's for sure, but I'm confident in my own ability and I've performed well since I've been at Coventry.
"I can only do what I can do and if it's good enough I will be in the team.
Marshall had an operation for a croneral injury of the ankle four weeks ago and remains very optimisitic of being ready for the new season. "So far it's going very well. The hardest thing is staying off it at the moment but things are positive and looking very good.
"The injury was a combination of wear and tear over the years and a few little incidents while playing.
"I spoke to the manager about it and he asked me if I could put it off until the end of the season which I did, as did a few of the other lads with similar problems.
"I'll hopefully be for a little bit after the start of pre-season but I'm hoping to be fit for the start of the season. I'll be about three weeks behind the rest of the lads."