To be exact, the service motion starts the minute you either start the toss, or move the racket from a motionless position, whichever comes first, and continues until you strike the ball. Any foot infraction during that entire time is considered a foot fault.
There is no debating the rules themselves, only the discretion of the linespeople. While it's easy to say that all rules can and will be called at any time, this simply isn't the reality (in tennis or any other professional sport). The officials make decisions when they make calls, not just about whether a rule was broken, but how it affects the match. Just as foul calls in an NBA game aren't made in a petty way at important times, and just as umpires in tennis try not to toss out players on random code violations, there is flexibility.
Before you all flame this post, let me present a related fact. In MANY pro service motions, players start with their front foot touching the baseline, then rotate the foot away as they start moving to avoid touching the line during the actual swing. In the spirit of Safin's foot fault, all of these would be foot faults, yet I've never seen it called. Mathieu does this in his motion. In yesterday's match, he and Grosjean BOTH did this almost every serve and yet were not called for it, nor have I ever seen either player called for it in the past.
Similarly, it was not the first time Safin had crossed the center line slightly by accident, but it is the first time he was called for it. Why did the official suddenly decide to call it in a way that decided the set? Bad judgement. While Safin isn't
entitled to a warning, it is actually common practice for an official to take a player aside during a changeover and say something quietly about such a thing before having it change the entire outcome of the match. That's just good officiating. No one wants a silly pettiness to affect the outcome of a match.
