LONDON - There is little time for the Premier League's stars to shake off their World Cup hangover as the chase to catch champion Manchester City begins in earnest on Friday.

On top of the quick turnaround from the World Cup in Russia, a shortened transfer window that closes 24 hours before the season kicks off has left many teams scrambling to get stronger at the last minute - none more so than Manchester United.

The Red Devils raise the curtain on the campaign at home to Leicester on Friday night, hoping to put a troubled preseason dominated by manager Jose Mourinho's outbursts behind them.

Mourinho has criticized the club's hierarchy for failing to sufficiently strengthen his roster, despite the signings of Brazilian international midfielder Fred and Portuguese fullback Diogo Dalot.

As United dithers, Liverpool has emerged as a top contender for the title behind City after splashing over $220 million on goalkeeper Alisson and midfielders Fabinho, Naby Keita and Xherdan Shaqiri.

"The other clubs who compete with us are really strong and already have fantastic teams, or they are investing massively like Liverpool, who are buying everything and everybody," said Mourinho.

"If we don't make our team better it will be a difficult season for us."

United is further hamstrung with a host of key players, including Paul Pogba, Romelu Lukaku and Marcus Rashford, who were involved in the later stages of the World Cup, limiting their preseason preparations.

Reds hot

By contrast, Liverpool is well placed to hit the ground running ahead of Sunday's home opener against West Ham as Virgil van Dijk, Keita and Fabinho were missing from the World Cup, while Mo Salah and Sadio Mane bowed out during the group stage with Egypt and Senegal, respectively.

Jurgen Klopp's Reds demonstrated their ability to beat City on the big occasion last season, winning three of the four meetings between the sides, including a 5-1 aggregate win in the Champions League quarterfinals.

However, Liverpool finished 25 points adrift of City in the league as Pep Guardiola's squad romped to the title with a record 100 points.

"The players from last year are responsible for the excitement, and then we brought in a few new players as an icing on the cake," Klopp said during the club's promising preseason tour in the United States.

"It's not just that we have to be more consistent, we have to create circumstances where we can be more consistent," the German added.

"Nobody is consistent with 11 players. What we are working on is the depth of the squad because you need to have that."

City still favorites

City hasn't dipped into the deep pockets of its Abu Dhabi owners as significantly as Guardiola's first two summers in charge, but has still strengthened with club-record signing Riyad Mahrez.

No side since United nine years ago has retained the title, with Chelsea (twice) and Leicester failing to even make the top four in the past three seasons.

Despite missing a host of World Cup stars, City looked in ominous form as it dismissed Chelsea 2-0 to lift the Community Shield last weekend but faces a tough start as Arsenal begins the post-Arsene Wenger era at Emirates stadium on Sunday.

New Gunners boss Unai Emery has enjoyed the luxury of having most of his squad available in preseason, with Pierre-Emerick Aubameyang, Henrikh Mkhitaryan, Mesut Ozil and Alexandre Lacazette forming a fearsome front four.

Chelsea also has a new boss but is already playing catchup with Maurizio Sarri only appointed a month before the start of the campaign.

The Blues swung into action on Wednesday when they agreed to sell goalkeeper Thibaut Courtois to Real Madrid in a deal that paved the way for Athletic Bilbao 'keeper Kepa Arrizabalaga to move to Stamford Bridge on a seven-year deal worth an estimated $92 million, becoming the most expensive goalkeeper of all time.

In contrast to the changes in west London, Tottenham in the north of the English capital has yet to add a single signing ahead of its first season in a new 62,000-seater stadium.

Yet, based on the World Cup performances of Golden Boot winner Harry Kane, Hugo Lloris and Christian Eriksen among others, there is still plenty for Mauricio Pochettino to look forward to.

Agence France - Presse