"There are 14 clubs in this division that think they can get promotion and this club is definitely one of them," he told BBC Points West.
"If you come in thinking you're going to aim for anything less then you'll have a season of mediocrity."
Wigley continued: "I look at the club and they obviously showed some ambition this summer by signing David James.
"This city could sustain a Premier League club and sooner rather than later."
And the England Under-21 coach had little hesitation in accepting the offer once approached by Millen.
"It was an easy decision to make," he said.
"I've been in a situation at Bolton where I'd been on gardening leave for a period of time and I was desperate to get back."
Wigley did have a brief period as a Premier League manager with Southampton back in 2004 and is in no rush to go back to that role.
"I've had no thoughts on being a manager for a long time and am more than happy with coaching," he added.
"My job is to help Keith and I believe I've got the experience to do so.
"I've met Keith on a few coaching courses and I back him to have a good career as a manager."
Source: BBC Sport
Source: BBC Sport