Untroubled through his first six sets of the fortnight, Federer now faces an opponent with an equally unblemished record through two rounds.  Whereas the third seed cruised past unheralded foes, though, Cilic dealt heavy blows to the hopes of promising youngsters Harrison and Cilic, either of whom would have seemed a more plausible challenger to Federer at this stage.  But the Croat has struck his inside-out forehand with devastating effect this week, and that weapon will prove vital in chipping away at the Swiss legend’s one-handed backhand.  Unable to seriously threaten Federer in their two previous meetings, Cilic has found his imposing serve neutralized by the former’s blocked returns.  Loath to finish points in the forecourt, this firmly rooted baseliner will find the initiative gradually wrested away from him as the world #3 exploits his ungainly movement.  Nevertheless, Federer has a mixed record against ATP sluggers in recent months, dominating Del Potro while falling twice to Tsonga and once to Berdych.  While Cilic surely cannot outlast him in a best-of-five format, he should force the five-time champion to raise his focus a notch or two if he wants to advance in straight sets.