NEW YORK — At this point in his career, Roger Federer recognizes the importance of a little extra work. That's why the owner of a record 17 Grand Slam titles, and the man who spent more weeks ranked No. 1 than any other, was out there on a U.S. Open practice court late Tuesday afternoon, putting in some training time shortly after finishing off a 6-3, 6-2, 7-5 victory over 62nd-ranked Grega Zemlja of Slovenia in the first round.