Paul Lambert says hours spent travelling to away matches may have contributed to Adam Drury's injury problems. The City left-back could be absent for the second time in three matches because of a calf injury picked up during the goalless draw at Queens Park Rangers on Saturday.

Drury missed the Bristol City game a fortnight earlier after suffering hamstring problems in the warm-up – and Lambert believes travelling could be a contributory factor.

'It doesn't help when you sit on a bus for seven or eight hours going down to Bristol,' he said. 'In football the knocks and that are normal when you play in a physical match, but when you're travelling that length of time on a bus it's not great.

'I'm pretty sure that had a bearing on it – it's the worst journey I think I've done in a long while, but to be fair to Steve Smith he came in and was excellent for us.' Smith is the obvious – maybe the only – candidate should Drury not make it.

'Adam was terrific last season and only really came out of the side through injuries and with Rhoys (Wiggins) going away I had to get somebody to come in and Steven came in and I thought was great on Saturday and was great against Bristol City. It's good cover.'

While Smith is preparing for his first home start, the make-up of the rest of the back four isn't quite as clear. Elliott Ward is suspended after collecting his fifth booking on Saturday, but Lambert won't reveal who's favourite to step in.

With Michael Nelson and Zak Whitbread both out injured, the like-for-like replacement is Jens Berthel Askou, but there is also a chance it could be Russell Martin who moves across from right-back.

The one certainty is that Lambert doesn't have much in reserve as far as defenders go: if Askou gets the nod, there won't be one on the bench.

Lambert admits it's a worry – but one he can do little about. He has five players out on loan, but all for a reason.

'Everybody thinks we have a big squad, but we haven't really,' he said. 'Tom (Adeyemi), Cody (McDonald), (Matt) Gill, George (Francomb) and Owain (Tudur Jones) are out on loan. That's five lads that are out and three of them are kids, and that's where the thing lies. We have to try and keep everybody fit.

'The young lads have not learned their trade yet – and Korey (Smith) has been exceptional. He is more mature strength wise and he's played a lot of games now. Korey is an exception.'

Smith was given his big break by Lambert soon after the manager's arrival in August last year – and he's taken the opportunity with both hands. Such is his impact that Lambert won't consider asking him to change his game to accommodate his opponent – even if it is someone like former Dutch international Edgar Davids, currently on Palace's books and likely to feature in George Burley's squad tonight.

'If you come up against somebody like that it's great for him, if Davids plays,' said Lambert. 'On his day Edgar Davids was one of the best players in Europe let alone anything else. Age catches you at times and Korey is young and hungry and has been terrific for us, so I don't think he will have any fear that's for sure.'