The 23-year-old moved to Eastlands from Middlesbrough in the January transfer window and made a seamless transition to the Premier League.
His form prompted a call-up to Fabio Capello's preliminary 30-man England squad and, although he failed to make the final cut for the World Cup, he was regarded as one of the country's most promising talents.
However, Johnson has started just five league games this season and admits he would consider moving on if the situation does not improve.
He told The Sun: "Every footballer has to think about it when the time comes.
"It is still early but I definitely would consider it."
Johnson was criticised by Roberto Mancini last week for believing his own hype, but the winger is adamant he can perform on a regular basis as a starter for City.
"Last season and in games at the beginning of this season I was still having an impact when I started," he added.
"With the players we have, it will be a rotation but I am full of confidence and I just want to be playing.
"I have got to train and get on with it, nothing is going to change. I have to keep the right frame of mind and get in the team because I want to play for the national team as well."
Source: Team Talk
Source: Team Talk