Paul Lambert says Norwich City will not tolerate any players stepping out of line in their personal lives.

The City manager was speaking in the wake of Chris Martin's court appearance for assault – a case that has been hanging over the player's head for months and which Lambert believes began to affect his form on the pitch.

The case was effectively closed on Friday when Martin was fined �1,000 by Norwich Magistrates – but Lambert says the Beccles-born Martin must not damage his chances of making a career out of football.

'I am glad it's finished,' Lambert said. 'You have to remember he is only a young guy, 22 years of age, and being a footballer it can be dangerous at times.

'You don't condone anything in any shape or form. If somebody steps out of line then you don't put up with it. But at 22 years of age I know it can happen, not just here, it can happen all over the place. But the football club won't condone any sort of violence.'

Lambert has spoken to Martin about the situation and has made it clear that second chances don't come around too often.

'I know what's been going on and I know what's happened,' said Lambert. 'He has got a great chance to make a career for himself and I think that's what he has got to weigh up.

'You very rarely get two chances at football, very rarely, and I think Chrissy had the wake-up of going to Luton (on loan) and he gets a chance here, and does great in the first year –but it is only one year, it's only a season.

'Realistically you have got to have another 15 years in the game if you screw your head on. If you don't there is always somebody there to take your place, always. Nobody will thank you going out the door when somebody comes in, it's your loss.'

The money and glamour and celebrity attached to football nowadays has seen players hitting the front pages almost as often as they do the back pages, but Lambert says that showing any lack of commitment to the game could ruin a career.

'I think if you aspire to be a top player you have got to sacrifice a hell of a lot of things, especially if you're a young one growing up because other distractions are out there, nightclubs and alcohol,' he said.

'You have got every distraction under the sun. If you really want to do it you have got to screw your head a bit and think in the short space of time you've got in the game and the lifestyle you can have then you have to think what is going to be in it for you. Not just you, but Chrissy has got a girlfriend and a baby so it is their future and the more money you can get and a lifestyle you can get it is better for everybody, the family and everything. And you become a role model for younger kids, that's what you have got to remember as well.'

Martin's court case came 24 hours after the player suffered a hamstring injury in training, ruling him out of the game at home to Doncaster Rovers tonight and perhaps for the next few weeks.

The timing of the injury couldn't have been worse for a player who has failed to score in his last 11 appearances and has just four league goals this season.

Lambert believes the court proceedings have had an effect.

'I think definitely it is a weight off his shoulders,' he said. 'On the outside you can be as brash as anything you want, it doesn't really bother you, but I bet you inside you are never quite sure. Hopefully he won't have to go through anything like that again, not just in his career, but in his life.'