By North-west correspondent Alex Stevens

Jamie Carragher revealed his disappointment at Mamadou Sakho over an alleged anti-doping violation.

The France international, 26, is being investigated by UEFA for allegedly failing a drugs test prior to the Merseysiders’ Europa League tie against Manchester United on 17 Match.

The centre-back has not been banned by Liverpool but will not be selected during the investigation, which is understood to be into the use of a substance used to burn fat and build lean muscle.

Liverpool legend and TV pundit Carragher delivered a typically forthright response to learning that Sakho had failed a drugs test.

“It’s a nightmare for the player,” Carragher told Sky Sports News HQ on Monday night. “I think he’s let himself and the club down badly, because he’s become a really important player.

“There’s serious questions to be asked of him. For a professional footballer, as in any sport, it’s not acceptable.”

Sakho has formed an increasingly solid centre-back partnership with Dejan Lovren over the last few months and it has been key to the turnaround in Liverpool’s form, which has put them on the verge of ending Jurgen Klopp’s first season with some silverware.

The Merseysiders travel to Spain on Thursday for the first leg of their Europa League semi-final against Villarreal but will have to do so without Sakho.

“He’s had a great campaign,” added Carragher to Sky Sports News HQ. “He’s one of the leaders of the team now, certainly within that run, thinking about how well he played in the Manchester United and Borussia Dortmund games. It’s now how Liverpool fill that void.”

Kolo Toure deputised for Sakho in last Saturday’s 2-2 Premier League draw against Newcastle and is contention, along with midfielder Lucas Leiva, to partner Lovren at Villarreal.

In other Liverpool news, Steve Nicol has identified who his former club will sign to replace Christian Benteke in the summer.