LONDON: Liverpool’s Europa and Premier League run-in has been complicated further by the potential lengthy suspension of central defender Mamadou Sakho for failing a dope test.

The 26-year-old French international was omitted from their line-up for Saturday’s 2:2 Premier draw against Newcastle after manager Jurgen Klopp learned he had failed a test after the 1:1 Europa League draw with Manchester United on March 17.

Liverpool won the tie and went on to beat Borussia Dortmund in the quarter-finals with Sakho scoring a crucial late goal as the Reds fought back for a dramatic 4:3 victory in the second leg. They face Villarreal on Thursday in the first leg of the semi-final.

The result of a B sample is expected to be produced by European federation UEFA on of Tuesday. Although the substance allegedly found in Sakho’s system has not been named, it is believed to be a fat-burner used to aid weight loss. It is thought Sakho will plead ignorance, believing he took a supplement which was not on UEFA’s banned list.

The maximum possible sanction is a two-year ban though Sakho’s Liverpool team-mate Kolo Toure received a six-month suspension in 2011 for using prohibited dietary pills while at Manchester City. He pleaded, in his own defence, that he had not been seeking intentionally to enhance his performance.

Liverpool released a statement on Saturday afternoon having learned of Sakho’s test the previous day.

It said: “UEFA is investigating a possible anti-doping rule violation by Mamadou Sakho. The player will respond to UEFA on the matter. ‘The player is currently not subject to any playing suspension. However, the club, in consultation with the player, has decided that while this process is followed the player will not be available for selection for matches.”

Klopp, speaking after Saturday’s game in which they threw away a two-goal lead, said: “It is not the easiest situation that is for sure. All we can say about this, we will say when we know more, next week probably.”

Even if the dope test failure is confirmed it is the player, not the club, who would face disciplinary action. Hence Liverpool’s continuance in the Europa League is not under threat.

In 2015 Dinamo Zagreb midfielder Arujan Ademi failed a dope test after a 2:1 win over Arsenal in the Champions League group stage. The player was suspended for four years but Dinamo were not punished. Under UEFA rules the club is liable for punishment only if at least two players fail tests after the same match.

Sakho, an £18m signing from Paris Saint-Germain in 2013, has played 34 games for Liverpool this season, including 10 in the Europa League. He now risks not only missing the climax to Liverpool’s season at home and abroad but also the Euro 2016 finals in France in June and July.

The player, nicknamed The Eiffel Tower because of his size and power, has been among the club’s most improved players in recent months. His goals against Borussia Dortmund and Everton in the last fortnight have enhanced his cult status on The Kop.

Klopp denied Sakho’s absence was a factor in Liverpool’s four-game winning run ending against Rafa Benitez’s Newcastle after early goals from Daniel Sturridge and Adam Lallana. Newcastle, managed by old Liverpool boss Rafa Benitez, recovered through Papiss Cisse and Jack Colback.

Klopp said: “We have changed a lot of players in the last few weeks, a lot of centre-halves, so you can’t say we missed Mama.”

Injuries mean Liverpool are already without midfielders Jordan Henderson and Emre Can as well as Belgium striker Divock Origi for the Villarreal tie. Ironically, Toure took Sakho’s place on Saturday and could do so again in Spain.

English football is not considered to have a doping problem though there have been occasional cases: Rio Ferdinand was banned for eight months in 2004 after missing a drugs test; Jaap Stam tested positive for a banned anabolic steroid, nandrolone, weeks after leaving Manchester United for Lazio in 2001 and was banned for four months; and Portugal defender Abel Xavier, then with Middlesbrough, was banned for 12 months in 2005 after testing positive for the banned substance methandrostenolone.

A handful of other cases have centred not on performance-enhancing substances but on social drugs.