Mamadou Sakho will respond to Uefa’s investigation into his failed drug test on Tuesday when the Liverpool defender has to decide whether to have his B sample analysed.

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The France defender may face a lengthy ban for contravening Uefa’s drug rules in a test submitted after the Europa League tie at Manchester United on 17 March. A fat-burning substance is believed to have been discovered in the sample provided by the 26-year-old, who was dropped by the former manager Brendan Rodgers against Stoke City and Bournemouth at the start of the season for being overweight.

Liverpool were informed of Sakho’s failed test on Friday and the player was given a deadline of Tuesday to request that his B sample also be examined. The £19m signing from Paris Saint-Germain has not yet been charged by Uefa but the Liverpool hierarchy, including the manager Jürgen Klopp and chief executive Ian Ayre, have decided not to consider him for selection while the investigation is under way.

Sakho, who had been in fine form before the controversy erupted, missed Saturday’s 2-2 draw with Newcastle United and will be absent again when Liverpool play Villarreal at El Madrigal stadium in Thursday’s Europa League semi-final.

One of his predecessors in the heart of the Liverpool defence, Jamie Carragher, believes that if Sakho is found guilty and banned, the former PSG captain will have let the club down by his actions.

Carragher said: “There seems to be a lot more of this that goes on in other sports. It’s not 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.

“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.”