Jamie Carragher says Mamadou Sakho has let himself and Liverpool down badly over an alleged anti-doping violation. Sakho, 26, is being investigated by UEFA for allegedly failing a drugs test prior to the Reds Europa League second-leg tie at Manchester United on March 17.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 fat-burning substance. Sky Sports football expert Carragher says serious questions must be asked of Sakho and any professional footballer who turns in a failed sample.Its a nightmare for the player, former Liverpool star Carragher told Sky Sports News HQ.I think hes let himself and the club down badly, because hes become a really important player.Theres serious questions to be asked of him.Hes had a great campaign. Hes 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. Its now how Liverpool fill that void.For a professional footballer, as in any sport, its not acceptable. Carragher, who made over 700 appearances for Liverpool during a 19-year senior career, also questioned whether footballers are given spot-doping tests regularly enough. Jamie Carragher has questioned whether players are tested regularly enough He said: How much is enough, or too much? As a player it would happen two or three times a season. People might say thats not enough.But there seems to be a lot more of that goes on in other sports, not something youd expect from football. Also See: Huge risks of fat-burners Toure backs Sakho Sakho probed Weekend ref watch Maxi Rodriguez Argentina Jersey . In what the team had called a retirement, Ryan said Thursday that he is resigning as chief executive of the Rangers in a move effective at the end of this month. Angel Di Maria Argentina Jersey . As the crowd erupted, Davis knocked the ball off the glass and back into his hands. With 1:14 to go in overtime, Davis sixth block also became his 17th rebound. That, along with his 32 points -- which tied a career high -- proved too much for Denver to overcome, and the Pelicans held on for their third straight victory, 111-107 on Sunday night. http://www.argentinasoccerauthentic.com/Nahuel-Guzman-Copa-America-Jersey/ . -- Tony Stewart is 20 pounds lighter and has a titanium rod in his surgically repaired right leg. Martin Demichelis Argentina Jersey . But what about the officials? Every sport has officials and they also have stories about hard work and sacrifice but their accomplishments are seldom recognized by anyone outside their inner circle. Ever Banega Jersey . -- The Bishops Gaiters are showing they belong among the countrys top varsity football teams. Greeny and Golic welcome ESPN NFL analyst Mark Schlereth (6:30 a.m. ET), Jets RB Matt Forte (7:05), Super Bowl XXXV champion Brian Billick (7:30), SEC Networks Booger McFarland (8:00) and ESPN MLB Insider Jayson Stark (9:30) to the show on Thursday.Get in touch with Mike & Mike by emailing (mikeandmikke@espnradio.ddddddddddddcom) or tweeting (@MikeAndMike) the guys -- we will be with you from 6-10 a.m. ET. Follow all of the action on ESPN2, ESPN Radio and ESPNRadio.com. ' ' '