Liverpool are preparing a summer raid on title rivals Manchester City for forgotten man Matija Nastasic, [football] direct news understands. The Serbia international has not featured for the Blues since the 1-0 home loss at the hands of Chelsea on February 3, and has baffled the club’s medical staff with an ongoing knee problem. City’s physios cannot find a problem and believe he is fit enough to play, but the 20-year-old insists he is still in discomfort and has been unable to rejoin his team-mates for full training. Nastasic’s reputation soared last season when he was one of their stand-out performers in an otherwise-disappointing campaign which culminated in the sacking of boss Roberto Mancini, who signed the player in 2012. Even before his injury he failed to rediscover his best form under Mancini’s predecessor Manuel Pellegrini, but Liverpool boss Brendan Rodgers remains a keen admirer and, according to a source close to Anfield, is anxious to bolster his defence this summer. He has a track record of giving young players a run in the first-team and is confident of helping Nastasic get back to his best. Watch the second leg of UEFA Champions League quarter-final: Borussia Dortmund face Real MadridRead more Liverpool transfer news.