I'm not sure how long your typical crew duty day is, I'm assuming you are thinking of a crew flying a route and landing at around 20 to 22 hours? The thing is, if you redraw that graph so that the left vertical axis goes from 0 to 100 (or a bit over) it would suggest an answer that looks very different. The dip in performance would look very slight. At worst, the crew is still funtioning at around 95% effectiveness. I'm sure there are plenty of other human factors that are likely to have a much larger effect than that.
One could argue that landing the aircraft at 95% effectiveness is pretty reasonable. Just a thought, Just This Once.
Of course, if you're worried about landing then, it looks like you just need to fly around for another eight or nine hours and you'll be almost back to 100%.