King's Lynn joint boss Gary Setchell is warning the Linnets must batten down the hatches in today's FA Vase fourth round trip to Norton & Stockton Ancients. (3pm)

Town will have to be at their best to book a last 16 place against the Teeside-based side who have beaten both competition favourites Spennymoor and two-time reigning holders Whitley Bay in Northern League action this season.

'It's probably the strongest step five league in the country,' said Setchell. 'I remember playing for Sudbury and we went to Bedlington Terriers in this competition. We won but that was probably the hardest game I ever had for Sudbury.

'It's always a good atmosphere against physical sides who don't give you anything.

'They will fancy getting further in the competition and you look at them and they have beaten Spennymoor and Whitley Bay so they deserve plenty of respect.

'Those first 20 minutes I think will be crucial. They will come at us, put us under pressure and try to break us and we have to be ready for that.

'If it is physical we have to match them and hopefully then we'll get a chance to play our football. I spoke to someone who knows the club pretty well and he says they are a decent outfit with a powerful midfield – but we will be aware of that.'

Lynn travel north with major injury doubts over 28-goal top scorer and captain Jack Defty (hamstring). Midfield duo Luke Thurlbourne (ankle) and Steve Spriggs (groin) are also carrying knocks but Setchell remains cautiously optimistic the key trio will be fit.

'Jack is the biggest doubt,' said Setchell. 'He is struggling, no two ways about it, but we spoke to him on Friday and he felt better.

'It's such a big game but I know Jack will be honest with us and if he is feeling it then he'll tell us because we can't afford to start him, then he goes lame, and we have to take him off after five or ten minutes.

'We have Chris Bacon eligible for this tie so that is an option. Spriggsy (groin) has been carrying his injury for a while but we don't think it is something that will get any worse. Luke is probably 60:40 in favour of playing.

'He took a hell of a bang against Wroxham and had to come off after only a few minutes but other than those three we don't have any other worries.'

Setchell admitted FA Vase fever is building with the club closing in on the business end of the prestigious competition.

'The lads are looking forward to it and I am as well,' he said. 'We have tended to perform in the big games and there is now a definite buzz around the players at training and the town as a whole. You can really sense it.

'The lads know it will take a lot of hard work, and maybe a bit of luck, but if we can get through and get a home draw then we can go a long way in this competition.

'You look at the other teams left now and it is a real high class of club at our level across the country. This is the nitty gritty and it's great to be a part of it.'