Manchester United and Chelsea appear to need a striker. Manchester City has a shortage of full backs. Arsenal’s transfer plans could hinge on whether Alexis Sanchez stays.

With six weeks to go until the Premier League begins, English soccer’s top clubs are gearing up for preseason training and in the process of reshaping their squads in what is set to be another offseason of heavy spending.

In 2016, the Premier League spent more than 1 billion pounds (now $1.3 billion) in an offseason transfer window for the first time, at least doubling the amount spent in any of the other big leagues in Europe.

Courtesy of AP, here’s a look at what last season’s top six in the Premier League are prioritizing this year:

ARSENAL

Retaining players, rather than signing them, appears to be Arsenal’s priority this offseason.

A failure to qualify for the Champions League makes Arsenal a less-attractive proposition to its big-name players, Alexis Sanchez and Mesut Ozil. Sanchez, in particular, would be a massive loss to manager Arsene Wenger after finishing last season with 24 league goals.

Until the futures of Sanchez and Ozil are decided, Wenger’s plans in the transfer market could be paralyzed. Lyon striker Alexandre Lacazette could be a realistic option.

___

CHELSEA

With Diego Costa recently revealing that he is no longer wanted by Chelsea manager Antonio Conte, there is an obvious gap that requires filling in the attack.

One of the biggest transfer stories in England currently centers on the possibility of Everton striker Romelu Lukaku making a return to Chelsea. Lukaku has been quite open about his future while on international duty with Belgium this month, saying that staying at Everton “is not really an option” and that he had reached an agreement with an unnamed club.

Chelsea is back in the Champions League after a season out of Europe, so Conte also will probably look to strengthen his options at wing back and central midfield.

___

TOTTENHAM

Of the top six, Tottenham has the most settled squad and no pressing concerns — provided that manager Mauricio Pochettino keeps hold of his best players.

Most intrigue surrounds the future of right back Kyle Walker, who was no longer assured of being first choice at the end of last season thanks to the emergence of Kieran Trippier. Walker, who is England’s starting right back, has been heavily linked with Manchester City.

___

MANCHESTER CITY

Manchester City was the biggest Premier League spender last year ahead of Pep Guardiola’s first season in charge, splashing out nearly 175 million pounds (now $225 million). The club is already on the way to topping that figure.

In has come Brazilian goalkeeper Ederson Moraes for $45 million and Portugal playmaker Bernardo Silva for $55 million.

City has made no secret of its desire to sign as many as three full backs following the release of right backs Pablo Zabaleta and Bacary Sagna, and left back Gael Clichy. Dani Alves and Benjamin Mendy are expected to be two of the full backs coming in.

Heavily linked with Arsenal forward Alexis Sanchez, it wouldn’t be a surprise to see Guardiola also bringing in a central midfielder.

___

LIVERPOOL

Juergen Klopp’s squad was undermanned last season when Liverpool only had domestic competitions on its schedule.

Now back in the Champions League, expect Liverpool to strengthen in most departments over the next two months so the team can make a challenge on two fronts.

The Reds broke the club’s transfer record to sign winger Mohamed Salah for an initial fee of $42 million ($46.8 million) last week and have brought in Dominic Solanke from Chelsea as a back-up striker.

Klopp is also in the market for a center back — Liverpool ended its interest in Virgil van Dijk after a complaint from his team, Southampton — and will surely sign a left back to avoid having to play midfielder James Milner there for a second straight season.

___

MANCHESTER UNITED

Manchester United is in the market for a striker after releasing Zlatan Ibrahimovic, who is sidelined by a long-term knee injury. That has left manager Jose Mourinho light up front, with only Marcus Rashford, Wayne Rooney and potentially Anthony Martial as options.

Antoine Griezmann appeared to be United’s likely replacement for Ibrahimovic but the France forward announced he would be staying at Atletico Madrid, with the Spanish club currently serving a transfer ban and unable to register new players until January. Real Madrid striker Alvaro Morata might be United’s chief target now.

There is also a doubt surrounding the future of Rooney, who struggled for game time under Mourinho last season.

United, which is back in the Champions League, already has signed Sweden center back Victor Lindelof from Benfica for 35 million euros ($39.4 million).