Kovac was officially unveiled as Bayern head coach on Monday, having moved to the Bundesliga champions to replace Jupp Heynckes.
Since joining Bayern, Kovac has been linked with a raid on his old club, with Croatia forward Rebic reportedly at the top of the list after spending two years working together.
Rebic - who scored twice - and Kovac masterminded Frankfurt's stunning 3-1 win over Bayern in the DFB-Pokal final last season.
Asked about Kovac's move and the possibility of joining him, Rebic told reporters: "I've been working with him for a number of years.
"He was very successful [at Eintracht]. He earned his place at Bayern.
"I'm a player of Eintracht and I'm only focused on the World Cup at the moment.
"After the World Cup, then we can talk [about my future]."
Eintracht Frankfurt & #CRO star Ante Rebic was asked about former boss Niko Kovac and talks of a reunion at Bayern Munich.— Sacha Pisani (@Sachk0) July 4, 2018
Said he’s only focused on Eintracht and #WorldCup@OmnisportNews pic.twitter.com/pPhjJW4yJH
Rebic was speaking as Croatia prepare for Saturday's World Cup quarter-final showdown against hosts Russia in Sochi.
Led by Zlatko Dalic, Croatia are viewed as dark horses to win the tournament as they look to surpass the achievements of the iconic 1998 team, who finished third in France 20 years ago.
Ivan Rakitic and #CRO team now out for training in Adler.— Sacha Pisani (@Sachk0) July 4, 2018
Really relaxed mood as they look to follow in the footsteps and surpass achievements of iconic 1998 #WorldCup team @OmnisportNews pic.twitter.com/yMlAncnYwj
"Football was different 20 years ago," Rebic said. "Now we're on a good path. We have great support. I believe in our team that we can do something similar."
As for the challenge in facing Russia, he added: "We have analysed them. We have to focus on ourselves. We have more quality in our team. We will set the tone."