edinson cavani struggled in both legs for psg against barcelona .
uruguayan striker 's scoring record in ligue 1 is n't what it should be .
louis van gaal prefers to work with young talent and cavani is 28 .
radamel falcao has struggled at manchester united after signing on loan .
cavani says he wants to stay at psg and he may not have much choice .
van gaal identifies ilkay gundogan as replacement for michael carrick .