West Brom manager Sam Allardyce says an embarrassing 5-0 defeat by Leeds United shows he has a "tougher challenge" to keep his new club up than he thought.

Allardyce had been encouraged by the 1-1 draw at champions Liverpool on Sunday, but saw his team outclassed by a Leeds side which was also promoted from the Championship last season.

The Baggies remain second bottom and are five points adrift of safety.

"Liverpool was fantastic, but this was dreadful," said Allardyce.

Leeds scored four goals in a rampant first-half display at The Hawthorns, but were gifted the opening goal when home midfielder Romaine Sawyers bizarrely passed into his own net from 25 yards.

From that point Leeds utterly dominated. Ezgjan Alioski's crisp drive and Jack Harrison's thumping close-range finish left Albion trailing 3-0, while worryingly devoid of ideas and confidence.

Rodrigo's deflected shot put Leeds 4-0 ahead before half-time - but there was no let up for the hosts after the break.

Another swift attack ended in Brazilian winger Raphinha cutting inside from the right and curling beautifully into the top corner for the fifth.

Former England manager Allardyce, 66, is still searching for his first win since replacing the sacked Slaven Bilic. In his first game in charge, West Brom were beaten 3-0 at home by Aston Villa on 20 December.

"I didn't think it was such a tough challenge when we played Liverpool but tonight it's made it even tougher than I thought it was by the way we collapsed," said Allardyce, who has never been relegated during spells in charge of Bolton, Newcastle, Blackburn, West Ham, Sunderland, Crystal Palace and Everton.

"Two sides who just got promoted, 11 v 11 and what a difference between the two.

"We need to make sure we don't dish up another performance like that."

Leeds, who were promoted back to the top flight in July after a 16-year absence, move up to 11th place with 23 points from their opening 16 games.

But Leeds head coach Marcelo Bielsa has warned his side must strive to perform more consistently in the Premier League after demonstrating all of their attacking flair.

"We have only been in this league for 16 games and there are still many challenges and many tests we have to pass before we can legitimately say we belong," said Bielsa.

"We have to keep doing the same and keep doing it over a longer period of time."

Swashbuckling Leeds provide a Bielsa masterclass
Two of the most recognisable managers in English football came head to head for the first time, with the contrasting styles of Allardyce and Bielsa promising to offer an intriguing clash.

In truth, it proved a mismatch as Allardyce's pragmatic approach was destroyed by Bielsa's attacking philosophy in a one-sided first half.

Opinion on Bielsa's methods appeared to be polarised in the reaction to his team's 6-2 defeat at Manchester United before Christmas, yet performances of this calibre fully justify why the Argentine will not alter his tactics - whoever the opposition.

And why would he? It is a style which has transformed Leeds from an average Championship team into a swashbuckling side which is catching the eye in the Premier League.

True, there might be the odd blip along the way - there were also heavy defeats against Leicester and Crystal Palace - but very few Leeds fans would want to see anything different.

Against Albion, they produced a masterclass of Bielsa's philosophy. Leeds held 75% possession, made 750 passes to Albion's 238 and had 14 shots compared to just four from their hosts.

United have now scored 30 goals in the Premier League this season, meaning the only newly-promoted team in the competition's history to have netted more after their first 16 games of a season was Newcastle in 1993-94 (31).

Not only are they impressing in an attacking sense though. While they have conceded 30 goals courtesy of those heavy defeats, the Whites have also kept six clean sheets.

Defensively they were rarely troubled by Albion, who mustered their only shot on target in the second half.

By that time the game was long gone after Leeds' incisiveness was matched by top-quality finishing.

"It was a game where we defended well and we were efficient up front. From eight chances we scored five and that helped the result," added Bielsa.

"We played a serious game throughout and we managed the ball well, not committing any errors for them to attack us, apart from a few cases in the second half.

"Only two games ago we had an important defeat and our idea is to play in a consistent manner."

Bizarre own goal hampers Allardyce's Albion
While nobody can argue Leeds did not deserve to win by such a scoreline, Albion will rue the bizarre own goal from Sawyers which swung the match in the visitors' favour.

Under little pressure after the home side had won back possession in their own half, Sawyers attempted to play the ball back to Sam Johnstone without looking. However, the Albion keeper was out of position as he had moved out left to try and give an easier option to Sawyers.

Allardyce could scarcely believe what he had seen, slumping back into his dugout seat with his arms folded as he saw his gameplan ripped up inside 10 minutes.

"The own goal is a mistake, Romaine thought the keeper was there but he should have looked," Allardyce said.

"It was the last thing we wanted. Before I came we were riddled with conceding early goals and this time we gave them a Christmas present."

The Baggies showed organisation, resilience and fight to earn a point against Liverpool. None of that was evident against Leeds.

Allardyce had named the same starting XI which played at Anfield, explaining he wanted to build consistency and reward the players who fought hard to earn that point.

Yet it appeared to backfire as they looked sluggish and unable to cope with the energy of a vibrant Leeds side - who themselves were unchanged from Sunday's gritty win against Burnley.

After Sawyers' error, Leeds sensed Albion's deflation and seized their opportunity to wrap up victory before half-time. Positives were few and far between for the home side, although they did manage to limit Leeds to just one more goal after the break.

"I was shocked to see such a poor performance and we have to work hard to put it right," said Allardyce.

"Consistency is everything for us. We can't seem to get a consistency of attacking and defending right.

"When we lost the ball and tried to defend we were terrible, we have got to get that balance right in the transition. Life will get difficult if we cant get results quickly."

Man of the match - Stuart Dallas (Leeds United)

Albion needing another great escape? - stats of the day
West Brom have won just eight points in the Premier League so far this season, only amassing fewer after 16 games of a top-flight campaign in 1985-86
Leeds have now won seven of their 16 games in the Premier League this season, only six newly-promoted teams in the competition's history have picked up more victories at this stage of a season
West Brom manager Allardyce has lost consecutive home games by three or more goals in the Premier League for the first time since November 2007. The previous time came when he managed Newcastle United (4-1 against Portsmouth and 3-0 against Liverpool)
Leeds equalled their biggest margin of victory in a Premier League game, winning by five goals for the sixth time in the competition. It was also their joint-biggest margin of victory away from home in their league history
Leeds led by four goals at half-time in a Premier League game for the first time since May 2001 against Bradford City. The Whites led 5-1 at half-time, going on to win 6-1
Jack Harrison has been directly involved in seven goals for Leeds United in the Premier League this season (three goals and four assists). The only English midfielder who has had a direct hand in more this term is Aston Villa's Jack Grealish (11)
Since the start of last season, no side in the top four tiers of English football has scored more own goals in league competition than West Brom (seven, level with Southend United)
What's next?
Leeds travel to Tottenham on Saturday (12:30 GMT), with West Brom hosting Arsenal later on the same day (20:00 GMT).