Refuse to call it after 1 season at a new club in a new league. Make no mistake he has been truly awful and his attitude seems to be a massive problem. as people have mentioned he's the quintessential "Too much, too soon" young starlet rolling about in fancy cars and going clubbing instead of focusing on what is, a very short career where if he aspires to be the best, he has to make sacrifices for, and at the moment it doesn't seem like he wants to do that.
something i posted before though earlier in the season, is that because he seems to have bulked up a considerable amount of mass before the season started, I believe it has seriously hampered his game and he has failed to adapt to his new weight. especially in a sport like football, excess bulk regardless of if its lean muscle or not, will hit a point where it becomes more of a hindrance than a positive.
His movement seems sluggish, whilst he seems quite strong he also looks off balance during his take ons. he seems to have lost a yard of pace which looked to be a part of his game at the world cup. So all and all in addition to having to adapt to a new home, new surroundings, better players etc He's also having to relearn his game to his new build, and redevelop those attacking instincts.
Ill use the example from basketball i used before, Raptors center Jonas valanciunas a couple of seasons ago went on a Strength and conditioning program where he put on another 8-10kg or so of muscle in order to improve his post game. but what actually happened is at 7 ft, that extra 10kg or whatever of bulk made him sluggish and killed a ton of his natural athleticism and his rebounding and everything went to shit for a bit.
If memphis slimmed down to a more suitable build for football (most footballers are incredibly skinny for athletes in general) i think he would begin to reclaim a bit of the form that saw us spunk 30m pounds on him.