Having played in just three tournaments this year, Federer said he was pulling out of the Madrid Masters after suffering a back problem in practice.
원문출처 : http://edition.cnn.com/2016/05/02/tennis/roger-federer-tennis-madrid-masters-back-injury/index.html?eref=edition
원문출처 : http://edition.cnn.com/2016/05/02/tennis/roger-federer-tennis-madrid-masters-back-injury/index.html?eref=edition