Kluft is the reigning world heptathlon champion
Sweden's Carolina Kluft will miss next month's World Championships in Berlin and the rest of the season after suffering a hamstring injury.
Kluft, the reigning world heptathlon champion, picked up the injury in a meeting on home soil on Monday.
"This is the worst setback of my sporting career," the 26-year-old told Swedish radio.
She is expected to have surgery this week, after which she will need around six months rehabilitation.
Kluft is unbeaten in 22 heptathlon and pentathlon competitions since March 2002, winning nine consecutive gold medals in major competitions, but chose to compete in just the long jump and triple jump in last year's Olympics.
She finished ninth in the long jump but failed to qualify for the triple jump final in Beijing.
She said earlier this month that she would be concentrating on the long jump this year.