Jamie Carragher has claimed that Mamadou Sakho has let himself and Liverpool down after failing a drugs test.
The 26-year-old could face up to one year on the sidelines if found guilty of taking a banned substance.
Sakho tested positive during a routine drugs test following Liverpool's 1-1 draw with Manchester United in the Europa League on March 17.
UEFA is investigating the anti-doping violation, and during that time, Liverpool have opted to make the defender unavailable for matches.
The French defender has until Tuesday to decide whether to request that his B sample is tested, but faces a lengthy ban if found guilty.
"There seems to be a lot more of this that goes on in other sports," Carragher told Sky Sports News. "It's nothing something we expect in football, but in terms of his situation, it's a nightmare for the player. I think he's let himself and his club down badly, because he was becoming a really important player for Liverpool.
"There are certainly questions to be asked of him, because he's let himself down badly. He's had a great campaign. He's one of the leaders of the team now. You think of the Borussia Dortmund game, the Manchester United games especially, how well he played in those.
"It's how Liverpool fill that void. But for a professional footballer - or any sportsman, really - it's not acceptable."
It has been reported that Sakho tested positive for a 'fat burning' substance.
