Crystal Palace manager Sam Allardyce has refused to rule out the prospect of Mamadou Sakho joining the club on a permanent basis when his loan deal expires at the end of the season.
The French defender was banished from the first-team squad under Jurgen Klopp at Liverpool, but has helped Palace keep back-to-back clean sheets for the first time this season in his maiden two appearances for the Eagles.
Allardyce also credited fellow January arrivals Patrick van Aanholt and Luka Milivojevic for his side's defensive improvement, but admitted that it would take a "big negotiation" to sign Sakho for good this summer.
"I think two people on this front, Luka and Mama have given us more defensive resilience. We are more defensive in terms of the capabilities of looking after the opposition's attacking forces have been improved by those two players and Patrick. We have found that we are more difficult to score against which has been one of my first aims, my first targets ever since I first came here," he told reporters.
"Once we began to do that we began to win football matches and three wins out of five have all come because we can keep clean sheets so the basis of our defensive unit has grown and got better and that has been a good way forward for us to get out of the trouble we are in. Mama has played a big part in that, as have Luka and Patrick, and the whole team as a whole are defending better.
"It would be a big negotiation [to sign Sakho] at the end of the season if we were to stay in the Premier League. At this moment in time Mama has chosen crystal Palace to play first-team football, I think he has settled into the environment exceptionally well.
"He has worked extremely hard at getting himself fitter because he had not played a competitive game all season and he has shown what a good defender he is, and his capabilities on the ball - in possession he has been exceptionally good."
Palace, who currently sit just one point and one place outside the relegation zone, will welcome Watford to Selhurst Park on Saturday.
