That's hard to say. He'd have to fight Wilder for the answer. Parker is big with talent, but he has regressed a bit. He's good enough to beat the top 8-15 guys, such as H Fury, and A. Ruiz.
Parker for me is borderline world level. I'd pick AJ, wilder, povetkin and uysk to beat him. 50/50 with Ortiz, breazeale, miller and whyte. He's decent all round besides his poor footwork.