Because this season was a bit of a fluke season from them, and they were a high 90s team with city the past 5 years. Last season they made the final of every cup and were 1 point away from the league. A hangover after that season combined with some aging players that just need a bit of a refresher had a big impact, but a rebound after this season is fully expected.
They don't need 5-6 players, they got Diaz back from injury and they just need a couple of midfielders and they'll be back up there next season more then likely.