Now 26, the Republic of Ireland international suffered the heartache of being shown the door by then City boss Kevin Keegan as a teenager, and the lesson that setback taught him is one which continues to drive him forward.
Dreams of playing Premier League football were shattered as Westwood started the process of resurrecting his career in the Conference with Carlisle, and he admits that in many ways, it was the best thing that could have happened to him.
He said: "Obviously Manchester City is a massive club and when you are there as a kid, you get a bit side-tracked with stars in your eyes because you are training with people you have watched growing up.
"Being released was a big eye-opener and something I needed. Maybe if I hadn't been released, I wouldn't be where I am now.
"I have done things the hard way and it gives you that hunger and desire to achieve.
"Being let go as a young boy at Manchester City at 19 was obviously a kick in the teeth, but the kick up the bum I needed to kick-start my career."
Westwood's exit from City prompted an often frustrating search for a new club, and he was in the process of applying to join the police force when then Carlisle boss Paul Simpson handed him a lifeline.
He said: "I had a really bad summer getting passed from pillar to post, on trial here, on trail there and nothing ever working, being promised contracts and then having them taken away.
"It was one of those summers. I was close to being a policemen, signing up for the force.
"I was filling out forms, and then I got a call saying, 'Come up to Carlisle'. I did and have not looked back, really.
"From that day, I have said to myself, 'Look, to get anything in this life, you have to work hard and try to achieve it'."
Westwood will go head to head with Belgium international Simon Mignolet for the chance to win a place in the Sunderland starting line-up for the opening day trip to Liverpool next month as Craig Gordon continues his recovery from knee surgery with his long-term future a topic for debate.
It is a battle he is relishing, although he knows there is only one way he will get the nod from manager Steve Bruce, whose side will play its first pre-season friendly at York tomorrow night.
He said: "He doesn't promise anyone anything. You have got to go out and earn your place and then perform well to stay in the team.
"It's the same in every position. In a Premier League squad and a Premier League team, no-one is ever guaranteed anything.
"You have to work hard to achieve that."
If the competition at Sunderland is stern, the man standing in Westwood's way on the international stage has proved a largely immovable object over the years.
Shay Given, who had a spell on loan on Wearside before joining derby rivals Newcastle, enjoys legendary status in Ireland and despite his difficulties at current club Manchester City, remains one of Giovanni Trapattoni's blue-chip boys.
But Westwood, who made a first competitive start for his country in place of the injured Given in March's 2-1 Euro 2012 qualifier victory over Macedonia in Dublin, is determined to oust him on a regular basis.
He said: "Shay is Shay. He's a great fella and a great keeper.
"I have been chipping away at him for the last couple of years. Taking that next step was obviously a big personal thing, and that next level is something that will take care of itself in due course."