Chelsea are unsure over whether to press ahead with a move for Jhon Durán despite being given permission to discuss personal terms with the Aston Villa striker.

Villa are ready to offload the Colombian, who is valued at £40m. Some at Villa are believed to have raised questions about his attitude and Chelsea are conducting background checks. His wage demands are another potential obstacle. Chelsea have been trying to cut their wage bill and have adopted a policy of handing out long and heavily incentivised contracts.

They have been tracking the 20-year-old for a while, though, and there remains a good chance the deal will go through. That would be welcome for Villa, who are looking to raise funds to boost their profitability and sustainability position before pressing ahead with signings.

Villa have been in discussions with Chelsea over a deal for Conor Gallagher and have also registered an interest in the Netherlands left-back Ian Maatsen, who has a £35m release clause. Maatsen, who is a Chelsea player, spent the second half of last season on loan at Borussia Dortmund and is up for sale.

Rival clubs believe PSR considerations have left Chelsea under pressure to sell players before the accounting deadline of 30 June. That has been denied at Stamford Bridge. They are, however, keen to move players out and are looking for buyers for Armando Broja, Trevoh Chalobah and Maatsen but are determined to fend off Bayern Munich’s interest in Levi Colwill.

Signing a striker is a priority for Chelsea, who want to provide competition for Nicolas Jackson, and they are also competing to sign Crystal Palace’s Michael Olise. The Palace winger’s contract contains a release clause of about £60m. Chelsea contacted Palace to find out more about the clause this week but doubts have emerged over whether Olise would favour a move there when there is also interest from Arsenal, Bayern, Newcastle and both Manchester clubs.

Chelsea will not give up – their scouting department is said to love the 22-year-old – although signing Olise would raise doubts over Noni Madueke’s future. There have been suggestions that Madueke could be offered to Palace as part of a deal.

Meanwhile, Adam Lallana has returned to Southampton from Brighton on a one-year contract following the club’s promotion to the Premier League.

Lallana made over 250 appearances for Southampton between 2006 and 2014 and captained the club before moving to Liverpool in 2014. “I’m extremely happy to come back to where it all started,” said the 36-year-old former England international. “Although it sounds like a bit of a fairytale, in my head there’s still a job to do and I’m really confident I’ve still got a lot to give to this football club.

“When I started speaking to Russell [Martin, the manager] and understood there was a little bit of interest, it was something I knew straightaway felt right in my head and in my heart that it was something I needed to pursue, and it came through in the end.”