De Jong, 26, hadn't featured on the ATP Tour since beating Samuel Heredia at the Davis Cup qualifiers in September. The Dutchman, ranked 102nd in the world, played in two more Challengers in September, but retired from his last match against David Jorda Sanchis in Porto on September 29th.
On Wednesday, one month after his last match, De Jong explained that he's been struggling with an injury that's gotten worse over time.
"I want to give an injury update, as not many of you may know I've been struggling with pain in my heel/Achilles since the first match of the season," De Jong said on Instagram.
"Some days were better than others, and I was able to play a lot of matches on adrenaline or without pain at all. But from August onwards, it got worse, and you could see a big bump on my heel, which was bothering me a lot. So it was time to find out what was wrong."
De Jong continued by announcing that the injury and required surgery will keep him out of action for half a year.
"After examination, it was shown that there's an extra piece of bone that is pinching my Achilles tendon, which has a vertical tear in it. Unfortunately, that tear won't heal as long as the bone is like this.
"So I've made the difficult decision to undergo surgery in mid-November and make my comeback once I'm eligible for a protected ranking, which will be at the start of April."
De Jong reached a career-high ATP ranking of 71st in January 2026 and impressed at this year's French Open, reaching the fourth round as a lucky loser and eventually losing to Alexander Zverev.
