He has had two fourth seasons in his managerial career.
Valencia, 2011/12: finished third, same as the previous two seasons. Made Europa League Semi-Finals, the furthest he ever got in a cup competition with them.
Sevilla, 2015/16: finished seventh, two places lower than he had done in both the previous two seasons. Made Copa del Rey Final and won the Europa League for the third straight year.
I mean, it doesn't sound like a catastrophic drop-off, to be honest.