While McManus has been mostly out of favour since Mowbray took over from Gordon Strachan in the summer, Fox was brought to Celtic Park in the close season for a reported fee of £1.5million and has been a regular when fit.
The former Hibs and West Brom boss explained that neither move has anything to do with the players' respective abilities, but would allow him to further refurbish his squad - the latest addition to which is striker Morten Rasmussen, who arrived on a three-and-a-half year deal from Brondby for an undisclosed fee.
"I am not resigned to losing Stephen," he said.
"I think it is an opportunity for him.
"I will put on record what a fantastic man he is and what a fantastic player he has been for this club and if this deal doesn't happen he will be back on the training ground and striving to get himself in the team.
"He is a great leader of men and they are in shortage but this is an opportunity for him and something that he is exploring and we will wait and see what develops.
"I have just brought in two young centre-halves recently (Josh Thompson and Thomas Rogne), I have brought in Jos Hooiveld, who is left-footed, and I have Darren O'Dea back from Reading.
"If he goes, I'm sure he will do very well.
"If he doesn't go, as I said, he will be competing to be in the team and I wouldn't put it past Stephen to see him at the heart of our defence for the rest of the season."
Mowbray then waxed lyrical about Fox, saying: "An opportunity has arisen for Danny.
"I get on very well with Brian Laws, I played with him at Middlesbrough many years ago, we had a conversation and I put the opportunity to Danny. It allows me a bit of flexibility in this window to move things around.
"But what I will say about Danny Fox, if nothing happens at Burnley for Danny then there is every chance that as soon as he is fit and available - he's a week or so away now - he will be featuring at left-back in the next game because he is a quality footballer."
Asked if he considered Fox's time at Celtic to have been a success, Mowbray replied: "I think so. He's a player of high quality but I have to make decisions.
"I have Paul Caddis, Lee Naylor, Darren O'Dea and Mark Wilson, who has played Champions League football at left-back. So there's four players who can play left-back.
"It's about flexibility for me and trying to prioritise the squad."
Mowbray expects new signing Rasmussen to make an appearance at some stage in the Scottish Premier League clash with Hibernian at Celtic Park.
"There's a fair chance Morten will be in the squad of 18 and a fair chance he will be on the pitch," he said. "I am delighted that we could add to the options up front.
"He's a different type of striker to the ones that we have got.
"Hopefully, given the opportunity, he can score goals which will obviously help the team."
On the subject of Motherwell's Paul Slane, a reported target of Mowbray, the Celtic boss said: "Paul Slane is a young player who is not in my domain.
"There are other parts of the football club who would be dealing with Motherwell and it's not something I would get involved in."