Rory McIlroy tweaked his back during last week's BMW PGA Championship but caught fire through the weekend to win the tournament.
Now, perhaps, his luck with injuries has run out.
After feeling pain in his left knee, McIlroy got off to a horrendous start in Friday's second round at the Memorial Tournament, shooting seven-over par through the first 14 holes at Muirfield Village Golf Club in Ohio.
That score included three consecutive double-bogeys.
McIlroy spoke about his tender knee after Thursday's first round, which he finished at nine-under.
"The inside of it is sore, it's a little swollen," he said, adding: "Hopefully it will be OK for tomorrow."