Liverpool defender Sebastian Coates has been ruled out for up to six months with a knee injury giving boss Brendan Rodgers a transfer headache. The centre-half suffered a tear in the anterior cruciate ligament of his right knee in Uruguay’s friendly against Japan last week. Coates who had been linked with a switch to Fulham this summer will have surgery on Friday and faces a long spell on the sidelines. The tall defender has made just six Premier League starts for the Reds scoring just one goal – although it was a screamer. Remember this stunning overhead kick in the 3-2 loss to QPR in March 2012? The injury throws into doubt the proposed loan move of Martin Skrtel to Napoli with Rodgers reluctant to leave himself short of options. The Reds could now step up their pursuit of long-term target Thiago Llori of Sporting Lisbon who is stalling on a new contract. Meanwhile Aly Cissokho trained with his new Liverpool teammates on Tuesday for the first time after sealing a season-long loan move from Valencia. The French defender passed his medical on Monday and will offer competition for Jose Enrique at left-back. Cissokho 25 is excited to join Liverpool and the Reds have the option to make his switch permanent for £4million next summer. He has played for a number of top European clubs and has Champions League experience with Porto Lyon and Valencia.