Mediocre:
of only moderate quality; not very good.
"a mediocre actor"
synonyms: ordinary, average, middling, middle-of-the-road, uninspired, undistinguished, indifferent, unexceptional, unexciting, unremarkable, run-of-the-mill, pedestrian, prosaic, lackluster, forgettable, amateur, amateurish; More
informalOK, so-so, ‘comme ci, comme ça’, plain-vanilla, fair-to-middling, no great shakes, not up to much, bush-league
"a mediocre performance"
Does that not explain the past 5 or 6 seasons?