He's definitely worth a pickup. Some reports say Best is considering ending his season to avoid any more chances of a concussion, other sources say he's probable for this Sunday. Either way, Morris is without a doubt worth a bench slot the rest of your season. (In deep leagues Keiland Williams is worth a look as well).
I wouldn't say for the long term, but short term in deep leagues ins't bad at all. I wouldn't expect much through the running game but in the passing game.. just like how Best was getting his points. I like him even more with Harrison out. I think think they will observe Best very closely since this is his 2nd concussion this year. Concussions are very tricky.