LENZERHEIDE, Switzerland—Roger Federer said Saturday any tournament comeback from his knee surgery last year will not be until at least the late summer. The 40-year-old tennis great gave an update on his lengthy rehabilitation to Swiss broadcaster SRF when he attended a women’s World Cup ski race at Lenzerheide, where he has a home. It confirmed Federer’s comments in November that he would not return in time for Wimbledon in June, though he did not specify Saturday his plans for the U.S. Open which starts Aug. 29. Federer told SRF his rehabilitation was progressing well enough that he was now thinking in terms of playing again. Previously, he said the motivation for undergoing surgery last August was to protect his future quality of life with his family rather than return to competitive tennis. Federer’s 20 Grand Slam singles titles are tied with Novak Djokovic and now one fewer than Rafael …