Since his first senior cap with Croatia in 2013, Kovacic has featured alongside Modric in one of international football's most formidable midfield partnerships.
The pair became club team-mates at Real Madrid in 2015 when Kovacic made the switch from Inter, and the current Chelsea man told GOAL in the latest episode of Box to Box how his relationship with the veteran playmaker has blossomed.
"My relationship with all the players is amazing, especially with Luka [Modric]," Kovacic said. "He was my idol when I was a child and then when I came to Madrid, we obviously connected more and now we share this friendship. It's amazing to have such a big player and big person as a friend. He has a big influence [on me]."
PumaWhen quizzed about a particular piece of advice given to him by Modric, Kovacic replied: "There were many, but if I need to choose one, [it] is when you play good, don't be too arrogant, and when you're not playing so good, you don't devastate yourself. Be confident. Have always the head high and do your best on the pitch."
Of course, it wasn't just Modric that featured in that famed Madrid side.
Alongside a host of world stars, Kovacic played with the imperious Cristiano Ronaldo, who he feels helped lead him both on and off the pitch.
"I was only 21 years old and there were some big players but, in the beginning was, I was a little bit nervous.Training was tough, tough, tough and it was always competition," the Chelsea midfielder admitted to GOAL while speaking at a PUMA event. "When I look back now, it was a huge pleasure to have such big players around me and I learned a lot.
Puma"I learned a lot and there are a lot of great characters. Of course, with my relationship with Luka, he was one of the leaders there and then you had up front [Cristiano] Ronaldo. He was a leader on and off the pitch."
Now 28 years old and with a wealth of experience, Kovacic has become one of Chelsea's most important midfielders.
Alongside a Champions League, Europa League and UEFA Super Cup under his belt, the Croat won the club's goal of the season in 2021-22 for his audacious volley against Liverpool.
Kovacic told GOAL that he considers it the "most beautiful" strike he has ever scored.
"The goal against Liverpool was amazing and it was just pure instinct," he said. "I saw the ball coming from the air and then I was not sure if to control it or to shoot. Usually I control it and this time thanks to God, I shoot it and it went in. So i think it’s my most beautiful goal that I have scored in my career."
Check out the full episode of Box to Box on GOAL's YouTube Channel.