The FA Cup defeat to Oldham was not the only problem that came to pass this weekend for Liverpool FC. Besides joining the long list of fourth round upsets, Liverpool have become terrifyingly aware of how desperately they need defensive depth. Liverpool lined up with Brad Jones in goal, Andre Wisdom at right back, Sebastián Coates and Martin Skrtel in the centre, and Jack Robinson at left back. This back 5 does not send waves of confidence through the bodies of Liverpool fans. Many may argue that despite the loss, it was only Oldham, so there was no need for a better lineup, but what will be worrying for Liverpool fans is that this was essentially Liverpool's second string, with one usual starter in Martin Skrtel. Rodgers' team have been put in this position through a combination of injury and lack of squad depth. The ideal starting back 5 of Reina, Johnson, Agger, Skrtel, and Jose Enrique sounds considerably better than the one listed above. The trouble is that Liverpool cannot afford to play those starters every game. Every good team needs backup players who can step up and do a sufficient job. That clearly did not happen at Boundary Park this weekend. Liverpool have already showed their heavy reliance on youth players this year with the emergence of Raheem Sterling and Andre Wisdom, but it is in these physical cup matches where a team needs a solid professional who knows how to get the job done. As mentioned above, injuries have played their role in forcing Brendan Rodgers to play such an inexperienced back line, but this should come as no shock to the Liverpool manager. Glen Johnson and Daniel Agger are no strangers to the Liverpool medical staff as they have amassed multiple injuries during their time on Merseyside, and although excellent when they play, it should not come as a suprise when they are injured or at least cannot play in fear of injury. Today Jamie Carragher celebrates his 35th birthday, and although this maybe a day of celebration, it should come as an ominous warning to Liverpool. Carragher is a Kop legend whose services to the club will never be forgotten, but it has increasingly become clear that in his older age he is not the player he used to be. With Carragher coming to the end of his career, there are not a lot of options at centre back outside of Agger and Skrtel. Some Liverpool fans may jump up and say "what about our other Uruguayan?" Well after that display by Coates, one can see why he has not broken into the first team. It may be argued that he lacked first team game time, but what the game showed was that although he may have some technical ability, he lacks physicality even with his 6'5" frame. Coates was regularly beaten in the air by Oldham's Matt Smith, and when you put a mammoth of man like Coates in, you expect him to use his body to his advantage. With Coates and Carragher not seemingly providing ample cover, it is clear that Liverpool must purchase a centre back. However, they need more than just one defender. Press "Next" to continue reading!