Sean Dyche knows Burnley are entering a crucial period of the season in their efforts to stay in the Premier League.
The Clarets have lost nine of their last 11 league games and go into Sunday's clash with West Ham three points adrift of safety and on the back of a home hammering by Everton.
After West Ham, Burnley face a key test at Huddersfield on January 2, while matches against Fulham, Watford, Southampton and Brighton follow over the next few weeks.
Boss Dyche said: "All games are important. But it's fair to say that it's a different story against some clubs than it is to others.
"There are a group of teams we have to challenge ourselves against and we're playing some of them in the next four games. Beyond that, there's a clutch of games over the next eight.
"We've got one of the big names in there, and then the rest are teams we'd like to think we should compete against."
Dyche had been renowned for making very few changes to his team, but this season has seen him tinkering with personnel and formation.
Initially, the Europa League prompted a rethink in approach, but lately it has been about trying to find a solution to Burnley's poor form and leaky defence, while coping with persistent injury issues.
Dyche said: "We're shuffling to try and get that mixture, that blend, that can be successful. I think that's an ongoing thing until people settle into the slots.
"We've got close to having the full squad available and every time we get there we've had injuries, and I don't think that's helpful.
"We've had situations where we've had no wide men available, we've had situations where centre-halves have been down with hernias – at one point two centre-halves.
"There's been a lot of challenges. Our job is to navigate our way through that and still find wins.
"We've attempted to do that, but we know the second half of the season is quite obviously very, very important."
Dyche has switched to a back five for the past three games, which worked reasonably well in defeats by Tottenham and Arsenal but was horribly porous against Everton.
Dyche gave a Premier League debut to Ben Gibson in that game, with the summer signing finally fit after two hernia operations, and he scored the Clarets' only goal before being substituted in the 63rd minute.
"He did fine," said Dyche. "We only took him off for a tactical change. Not an easy game to come into, that's for sure. I certainly wouldn't apportion too much on him about the result."
Another summer signing, goalkeeper Joe Hart, is one of only two ever-presents in the Premier League along with defender Ben Mee but, with Tom Heaton on the bench and Nick Pope nearly fit, Dyche stressed that no one is safe.
He said: "It's never in doubt that we look at every player on the pitch. There's very few players this season who have laid down such a strong marker where they're almost written on the team-sheet before it's even considered. Last season, I thought we had a lot of that."
West Ham are in contrasting form to Burnley having won five of their last six games to climb into the top 10, which is no surprise to Dyche.
"I think the only surprise with West Ham over the last few seasons is that they haven't been doing this because they're a good squad," he said.
"They spent a fortune in the summer and it's showing. There's some real quality there.
"They can still have days where they concede goals so they're certainly a team that you can attack and get at. But you've got to be wary of the fact they've definitely got an attacking threat."
