We just don't have the squad and quality to be a Top 4 team, the players that are stepping in just aren't performing, we rely too heavily on the same players and our mental strength is poor because we don't have leaders all over the pitch.
You can't underestimate how much having no Mings, Buendia for the whole season and losing Kamara, shot us to bits, then having Ramsey and Torres intermittently at best, whilst Diaby, Duran and Zaniolo have mostly struggled (when fit).