In a tournament recently, I noticed a player playing ridiculously slowly, at least a couple of minutes for a routine shot. This was consistent during the match.
At the end of this 2 and a half hour race to seven (it was probably closer to 3 hours and there were a total of 11 racks played in the match) the losing player congratulated the victor, but also mentioned to the victor that he should probably increase the pace of his game.
The victor of course said that it was a case of sour grapes and that he was just being a bad loser.
What should the loser have done? Bearing in mind that threats to be "put on the clock", were mentioned at the beginning of the tournament, but I have never seen it enforced.
You have to be prepared to make a compelling case to the TD.
If you get "a slow one" put the stop watch on him yourself. After three or four shots where he's racked up time per shot that is out of whack with other players in the event, you go up to the TD and present your evidence: actual minutes/seconds the guy is taking per shot. IOW, it's not so good to go say someone is "playing slow" because that can easily be dismissed as perception. Instead, go to the TD and say, "I just put the clock on the guy I'm playing and he took: four minutes, three and half minutes, and five minutes for his last three shots" and you're more likely to get a better outcome.
Of course, not all TDs are created equal. And some guys will go out of their way not to piss anyone off with a slow play ruling.
Lou Figueroa