West Brom boss Slaven Bilic heads into the Sky Bet Championship showdown with Leeds on New Year's Day stressing that a loss of focus could prove fatal for either side.
Leeds have taken over at the top of the table on goal difference, with West Brom failing to win any of their past three matches.
Both sides still have a healthy nine-point lead over third-placed Fulham but, after good winning runs throughout November, neither have been consistent in recent weeks.
"The league is very long and you know you cannot lose the focus because it happens every year," Bilic said at his pre-match press conference.
"If you lose the focus, commitment or quality – four or five per cent – then you are gone.
"Sometimes you can get lucky, but normally you pay the price for that."
Leeds' pulsating 5-4 win over Birmingham on Sunday was their first in four games.
But Bilic says Marcelo Bielsa's side have, like Albion, been galvanised by suffering semi-final play-off agony last season.
"They experienced something quite painful last year, they lost in the worst possible way," Bilic said.
"We did the same last season, you are there and then we lost it in the play-offs.
"They learn from their mistakes, you are double aware, double focused and that's definitely one of the reasons we are there with them and they with us."
Bielsa was grateful for the incredible victory over Birmingham, secured by a Wes Harding own goal in the fifth minute of injury time after Leeds had led on three occasions.
"I believe it is always better to win but winning does not guarantee too much in relation to the next game," Bielsa said.
"Always it is better to win, but to win is not enough to win again."
Leeds, who hope to have striker Patrick Bamford fit again, have not won at The Hawthorns since 2002 and have lost on their past three visits, including a 4-1 defeat last season.
Elsewhere on Wednesday, Fulham look for a third win in four as they host Reading, while Brentford – now fourth after defeat at Millwall on Sunday – travel to eighth-placed Bristol City.
City, for their part, will hope to build some momentum after ending their four-game losing run with a 3-0 victory over struggling Luton last time out.
Nottingham Forest and Sheffield Wednesday seek to tighten their grip on play-off places as they host Blackburn and Hull respectively, but Preston will be looking to pounce on any slip-ups as they take on Middlesbrough.
Bottom side Wigan, who have not won in 13 games, will hope to avoid any Birmingham backlash as they travel to St Andrew's, while fellow basement-dwellers Luton are at Millwall.
Stoke, in 21st, will aim to cut the seven-point gap to Huddersfield above them as they head to the John Smith's Stadium, and Wednesday's other game sees QPR take on Cardiff.