Crystal Palace manager Frank de Boer is unsure if the club will be able to complete the permanent signing of Liverpool outcast Mamadou Sakho before Thursday's (31 August) transfer deadline.

The French defender impressed hugely during a loan stint at Selhurst Park that came during Sam Allardyce's final few months at the helm, with his strong performances providing the catalyst for a big defensive improvement that helped Palace to avoid relegation from the Premier League.

Although a season-ending knee injury limited him to just eight appearances in south London, Sakho's importance was reflected in the fact that he was featured alongside the likes of Wilfried Zaha and Christian Benteke in a list of player of the year nominees.

Allardyce stated an interest in bringing Sakho back to Palace before his own departure in May, although conceded that any deal would be very costly with Liverpool said to be demanding £30m ($38.7m).

Managerial successor De Boer, who is already coming under serious pressure following a winless three-match run in which his side have yet to score a top-flight goal, has toed a similar line and last week conceded that he is "much too expensive" for the club to afford at this moment in time.

Palace were embarrassed in a heavy beating by newly-promoted Huddersfield Town on opening weekend and showed more resilience during a narrow loss at Liverpool. However, the Eagles' defensive frailties were exposed once again on Saturday (26 August) during a desperately disappointing 2-0 defeat to Swansea City, particularly after James Tomkins went off injured. To make matters worse, new signing Jairo Riedewald is currently sidelined with a groin problem.

Asked about the chances of signing Sakho this week following that latest home struggle, De Boer, who has tried to implement a three-man defensive system without success, told Sky Sports: "I don't know. We know what kind of impact he had last season. But for now, I can't say about it."

Palace spent £7.9m to sign Riedewald from Ajax in July, while Timothy Fosu-Mensah and Ruben Loftus-Cheek joined on loan from Manchester United and Chelsea respectively. De Boer acknowledged that they are looking for further high-quality new additions over the coming days.

"We are looking for players of course," he said. "But it has to really give quality to us. We will see. The club is focusing on the players that maybe we are going to get, and I am focusing on the team to get the right freshness for the Burnley game [on 10 September]."

West Bromwich Albion, Southampton, West Ham United, Napoli and AS Roma have also been linked with potential moves for Sakho, who has not played for Liverpool since April 2016 after falling out with manager Jurgen Klopp. Allardyce recently questioned why the centre-back was not given a second chance at Anfield amid the Reds' own well-documented issues at the back.

Mamadou Sakho
Mamadou Sakho proved an influential figure during his previous loan spell at Crystal Palace Reuters