When The Undertaker said his 'final farewell' to WWE at Survivor Series last year, the wrestling world was united in showing its appreciation to 'The Phenom'.

Fans, friends and even fellow Superstars all paid tribute to his incredible 30-year run in WWE.

Now, two-time WWE Hall of Famer Ric Flair has revealed what he said to The Undertaker following his retirement. 

Flair and The Undertaker were rivals on WWE programming for many years, with their most high-profile match coming at WrestleMania 18 in 2002.

However, behind the scenes, the pair share a deep mutual respect, as proven by the text message sent by Flair to The Undertaker late last year.

Per talkSPORT, the former 16-time world champion recently shared his words as part of an interview with Wrestling Inc. In the message, Flair was full of praise for The Undertaker. It read:

"Happy Thanksgiving Champ!! Thank you for carrying this business and setting the bar of greatness! The bar we all strived to reach and very few have even gotten close to!

"Then, now and forever you are ‘The Champ’!! So proud to call you my friend."

It perhaps not surprising the Flair holds The Undertaker in such high regard.

Their WrestleMania 18 match was one of Flair's first major bouts in WWE after a nine-year absence from the company and he spoke glowingly about The Undertaker's role in helping make the clash a success.

"That’s when Mark carried me, but we did have a hell of a match," Flair said of the pair's WrestleMania outing.

"In 2002, I’m 54, but we did have a hell of a match, which was great. After The Last Ride (documentary series), he talks about (how) he had some insecurities too.

"His were around health problems, bad back and stuff like that, which caused him to be insecure. Mine was all mental but we share that in common."

Despite the challenges both were facing, they went on to have one of the best matches on the show that night - one that is remembered fondly as part of The Undertaker's iconic WrestleMania winning streak.

Flair also went on to talk about how much others belief in his abilities has helped him over the years:

"Self confidence, no matter if it’s your body’s holding up or your mind and being able to do it and perform at the level that everybody thinks you can, it doesn’t matter how many times Hunter (Triple H) will say to me, ‘God damn it! You’re Ric Flair!

"Go out there and just relax. Be yourself.’ It goes in one ear, and it goes out the other.

"You shake your head and go ‘yes,’ and then you walk through the curtain and it’s just not there. And I think that is just due to being beating down for so long.

"I still really enjoyed some of that time and such great guys, Randy (Orton) Dave (Batista and) Hunter. How cool is that? Right?!"

Although Flair had some very kind words for The Undertaker after his retirement, it is fair to say that the feeling is mutual on the part of 'The Deadman'.

Both are professional wrestling icons, who built incredible legacies during their careers.

As Flair himself said in his text message, it is unlikely we will see many who make as big an impact in WWE as The Undertaker. The same also goes for Flair.