Rory McIlroy has withdrawn from next week's Memorial Tournament, his last scheduled warm-up event for the US Open, due to an ongoing rib injury.
McIlroy suffered the problem in the off-season after extensive practice sessions as he tried to decide on new equipment following former supplier Nike's withdrawal from the market.
It flared up as he lost a play-off to Graeme Storm at the BMW SA Open in January and he did not feature again until the WGC-Mexico Championship in March, where he finished four shots behind winner Dustin Johnson.
The Northern Irishman then played three further events before feeling discomfort at the Players Championship and undergoing an MRI scan, after which he was advised to take a "conservative approach" with his recovery.
That resulted in the four-time major winner pulling out of this week's BMW PGA Championship at Wentworth, an event he won in 2014, and now the Memorial Tournament at Muirfield Village.
"All focus is on getting back to full health for the U.S. Open," McIlroy's agent Sean O'Flaherty said in an email to Golf Digest.
The US Open takes place at Erin Hills in Wisconsin from June 15-18.