Former TNA World Heavyweight Champion Samoa Joe was recently interviewed by WWE Hall of Famer Jim Ross on his Ross Report podcast. You can check out the full interview at this link. Ross questioned Joe about signing with the WWE and he revealed his interest in joining the company to which he addressed as the "unchallenged challenge of his career."
It is worthy noting that the interview was recorded before WrestleMania 31. Joe confirmed people from WWE had reached out but called it informal and said nothing was set in stone. Since then, we've heard that Joe actually met with Triple H in Orlando and could be starting with NXT as early as June. Joe did not confirm this in the interview.
Joe also stated that he would be open to an NXT trail or a direct entry to the main roster. He talked about how he's never been wanted in any company he worked for but got work by proving himself. He added that if he has to start in WWE as an unwanted entity and prove himself, then that is what he's going to do.