Rune insists it is "not impossible" for the tennis great to add another major to his tally. When Djokovic won his record-extending 24th Slam at the US Open in September 2023, few would have predicted that he would not win one of the four biggest tournaments on the calendar in the next two years.
He reached only one final in that period, and that was at Wimbledon in 2024 when he was beaten in straight sets by Carlos Alcaraz.
The young Spaniard and Jannik Sinner have dominated the Grand Slam scene the past 24 months, sharing all eight majors between them.
Besides the Alcaraz and Sinner obstacle - Djokovic lost in three Grand Slam semi-finals against the pair in 2025 â- the Serbian also has Father Time catching up with him as he will turn 39 in May.
He will need to break the long-standing record of Ken Rosewall if he does win another major as the Australian was 37 years old when he won 1972 Australian Open.
Despite those hurdles, Rune insists you can never write off the former world No 1.
"What Novak is doing is impressive. In every tournament, he reaches at least the semi-finals, and people are talking about when he'll stop," he told Marca.
"You never know with Novak. What he's doing is already impossible, so if you ask me if it's impossible for him to win more Grand Slams, if you ask me about any other player his age, I'd say no, impossible, but if you ask me about Novak, I'll tell you that nothing is impossible."
Rune, of course, is hoping to catch up with Alcaraz and Sinner.
Just over two years ago, the Dane was touted as one of the sport's next big stars with many believing he would form the new Big Three along with Alcaraz and Sinner, but after peaking at No 4 in 2023, he fell away the following year.
And just when he appeared to hit form again - he finished runner-up to Jack Draper at the Indian Wells Open last March and beat Alcaraz in the Barcelona Open final in April - he was hit by a season-ending injury.
Rune snapped his Achilles at the Stockholm Open in September and was forced to undergo surgery that will likely lead to a six-month spell on the sidelines.
When asked what by Marca the difference between Alcaraz, Sinner and himself, he replied: "Before the injury, the main difference was consistency. Novak, Rafa [Nadal], and Roger [Federer] were able to do what they do consistently throughout the entire season.
"This isn't a skill you're born with; it's not talent, it's discipline! Years ago, I was ahead of Carlos and Jannik for a while, but I wasn't consistent and I lost that advantage.
"I was everywhere, I was young, perhaps my natural development was to go through this, and they became more and more disciplined.
"Now it's up to me to adjust my discipline, and the injury is a good start. You don't get through rehabilitation without discipline, day after day."
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