The idiom "Leader at the Back" means that someone is controlling or guiding a group from behind, rather than being in charge or taking responsibility. Full definition
Koscielny is old and injury prone now, we need a powerful commanding leader at the back and another two to compliment that in midfield before we can consider ourselves title contenders. (justarsenal.com)
What we need is an aerially dominant leader at the back who can organise a defence. (arsenalfcblog.com)
A real leader at the back, and he will an important figure for Tottenham as the defence looks to keep a clean sheet at Anfield on Saturday. (freshspurs.com)