Crystal Palace sign Mamadou Sakho from Liverpool but Oumar Niasse and Fredrik Ronnow deals fall through

New arrival is a boost to fans and provides Frank de Boer with a top-level, ball-playing defender but manager's future remains uncertain

Mamadou Sakho completed his desired return to south London for a structured £26m fee (Getty Images)

Crystal Palace completed the permanent signing of Mamadou Sakho in the early hours of Friday morning, but the transfers of Oumar Niasse and goalkeeper Fredrik Ronnow fell through.

It leaves the Eagles without any notable senior backup for Christian Benteke in attack - except Connor Wickham, who hasn't played in nearly a year due to injury - while the club failed to replace France international Steve Mandanda in goal.

Sakho's arrival, however, is a boost to the fans and provides Frank de Boer with a top-level, ball-playing defender. Liverpool eventually lowered their asking price to allow Sakho his desired return to south London for a structured £26m fee.

De Boer, who has lost all three of his opening Premier League games without scoring a single goal, still faces an uncertain future at Selhurst Park.

Palace have been considering potential replacements for the Dutchman, who has disappointed the club with his inflexibility and his inability to coach the squad into a new formation, having initially excited them with plans for expansive, attractive football.

Within the squad itself there were concerns over his man management and it is still not certain that De Boer will remain in place to take charge of another Premier League match.

For his part, De Boer had expected more high-quality signings but had been fairly warned that there was not an endless pot of cash.

Should De Boer remain in charge he must hope for no injuries to Christian Benteke, and should the Belgian go down he might be forced to play a midfielder as the focal point of his attack as he often did at Ajax.

Should De Boer leave then Dougie Freedman could be expected to take temporary charge and former England boss Roy Hodgson would be a frontrunner to be brought into the fold. The veteran coach is well-known to the Palace hierarchy, hails from the area and frequently attends games at Selhurst Park. An arch-pragmatist, Hodgson could be trusted to work with the personnel already at the club and find a shape to suit the best players.

The Eagles could asses the market for free agents, who are able to register after the transfer deadline in special circumstances.