Colback was not involved in the club's final pre-season friendly against Hellas Verona on Sunday.
"I think half of it is psychology", Shearer - who is one of the ambassadors for the event - told the Premier League launch show.
The United boss doesn't name and shame but it has been widely reported that Rafa Benitez had a number of players lined up to sign he believed at the start of the season, only for those players not to be got "over the line". "The most-important thing is that the team won and I'm also happy that I scored".
"This is a very hard negotiation but if I didn't think there was a chance I would say so".
"Sometimes they are unavailable and if they are available, sometimes the wages are not the same, the commission is not the same and the wages are huge". I try to manage and to improve the squad with the players who are available to make sure we are stronger than we are now.
"It's very hard because my Chinese is not good enough!" he joked (there has been reported interested from clubs in China). "If I decide to stay, it's for the city, the fans, the stature of the club, to stay in England and in the Premier League". "It is something you cannot control but at the moment I am fully committed to do the best that I can".
That's not to say the current squad is without talent and, with the likes of Matt Richie, Jonjo Shelvey and Dwight Gayle in their ranks, they already have a squad that compares favourably with the likes of Burnley, Brighton and Hove Albion and Huddersfield Town.
It is the shadow of history that is causing concern, and there remains an undercurrent of 2008, when the Newcastle owner Mike Ashley failed to back the then-manager Keegan.
"We are trying to move players out to bring players in". "That's what he wants and if he's not able to do that he won't be there for much longer. He's come here and not played in many games, but I like the player".
"We have a big squad and a lot of competition but I need to work hard and in the moments I am on the pitch, give my best", the Ghana worldwide explained.