But one that appears to have gotten the former unified heavyweight champion's attention is from former three-time heavyweight champion — and the last undisputed heavyweight champion — Lennox Lewis.

Lewis told Fighthype at the beginning of August that if Joshua doesn't fix the holes in his game, then Ruiz wins their Dec. 7 rematch in Saudi Arabia, "hands down." 

Joshua responded in a show titled 'AJ: The Untold Truth' on Sky Sports. In the video, Anna Woolhouse is talking with Joshua about how Lewis came back to avenge upset losses to Oliver McCall and Hasim Rahman, and Joshua cuts her off immediately.

"Lennox is a clown," Joshua quipped. "I don't respect Lennox."

Woolhouse came back and started to discuss Lewis' legacy, which includes victories over Mike Tyson, Evander Holyfield and Vitaly Klitschko, but Joshua cut her off again.

"So?" Joshua fired right back. "So am I. Me and Lennox are not the same. My legacy is to sit back and enjoy the younger generation coming up and not to be involved. Just to appreciate what it takes to get there. Lennox isn't like that. Me and Lennox are cut from a different cloth."

Lewis, who currently is an analyst for Fox Sports for their PBC broadcasts, responded to Joshua's comments on Twitter saying he is "disappointed" in his countryman and feels Joshua's more upset about his remarks on how Joshua handled past negotiations with WBC titlist Deontay Wilder.