11:26 AM PT -- Nadal just confirmed with reporters in London that he's pulling out ... explaining he simply can't serve with the injury.
He said he's saddened by the withdrawal, but admitted there was just no way he could win two more matches while injured.
He also said if he had somehow continued, the injury could have been made significantly worse, sidelining him from the sport for a far more lengthy period of time.
The dream Wimbledon final of Rafael Nadal vs.