Despite a rocky start in La Liga the Croatian is now widely considered as one the world's best midfielder having shone for Real Madrid and his country over the years.
And with his future at the Bernabeu under speculation amidst an expected overhaul under new manager Julen Lopetegui, Redknapp has shed light on how the 32-year-old's playing days could have taken another turn in the summer of 2011.
“The day after Manchester United lost to Barcelona in the Champions League final at Wembley in 2011, my dad received a call from Sir Alex Ferguson,” Redknapp wrote in his column for the Daily Mail.
“He wanted to sign Luka Modric. Xavi and Iniesta had raised the bar for midfielders. The best had to be players who could take the ball off either foot, dribble and pass through the lines.
“Having seen just how impressive those two were against United, Sir Alex identified Modric as the player to take his team forward.
“He would eventually leave Tottenham for Real Madrid the next year but only a few months after arriving at the Bernabeu he was voted La Liga's worst signing of the season by Spanish fans.
“It has always frustrated me that Modric has been so underrated. It is only when he adds goals to his game, such as his sensational strike against Argentina, that the rest of his game gets the recognition it deserves.”
Whilst a playing career at Old Trafford under Ferguson would most certainly have returned a number of honours, Modric has not failed to tick that box since leaving Spurs, having lifted four Champions League trophy's and a La Liga title with the Spanish giants.
The 32-year-old has been a focal point in Croatia's World Cup campaign to date, where he notched a sensational goal in the victory over Argentina which sealed their place in the Last 16 with a game to spare.