Former WWE Undisputed Champion John Cena appeared on the latest episode of Friday Night SmackDown and had a promo battle with his Clash in Paris opponent, Logan Paul. The segment ended with The Last Real Champion ducking a cheap shot from the YouTuber, turning it into Attitude Adjustment, and laying the former US Champion out cold.However, Cena still had a tough outing as, later in the show, Paul took his revenge. While Cena was leaving the arena, General Manager Nick Aldis stopped The Last Real Champion to tell him what he heard from Brock Lesnar. However, before he could have revealed anything, Paul struck a KO punch on Cena's chin, knocking him out.Meanwhile, following his appearance on SmackDown, John Cena has now posted a heartbreaking post on his official Instagram account. The 17-time champion posted a picture of soccer sensation Lionel Messi, wearing his number 10 jersey, which was also marked as his retirement match from Barcelona FC. View this post on Instagram Instagram PostWith the post, Cena indicated that he had only 10 dates left before he retired, and it wouldn't be easy for him either.John Cena is the greatest of all time, says top WWE Hall of FamerRecently, speaking in an interview with ESPN's SportsCenter, WWE's CCO and Hall of Famer Triple H dubbed The Last Real Champion as the greatest of all time and discussed Cena's retirement tour."John is the greatest of all time. And I think that this type of tour shows why he is. For him, this this sort of year-long tour is about him giving back. It's about him going to all these cities and towns that he has been that have made him one of the biggest WWE Superstars of all time, that have made him the Hollywood box office attraction that he is, that have made him so successful and helped him along that journey. This is him going back to them and saying thank you," He said.It will be thrilling to see what plans Triple H-led creative have in store for John Cena with only 10 dates left.