Hmmm, let me start this reply by saying that I'm one of biggest, most dedicated Nole's fans (since 2007). I wake up, if needed, at crazy early hours just to watch Nole's matches....
Having said that, the math from this presentation is horribly, horribly wrong. Every draw is an independent event. Hence, the probability for every new draw that Nole will play Federer is *always* exactly 50%. The draw has no memory and its probabilities do not change according to past results. So even if Nole drew Federer ten consecutive times, the probability that the next draw will produce Federer vs Nole matchup is still 50%.
People get confused because of the fallacy of the "law of averages". I'll paraphrase Wikipidia:
"As invoked in everyday life, this "law" usually reflects bad statistics or wishful thinking rather than any mathematical principle. While there is a real theorem that a random variable will reflect its underlying probability over a VERY LARGE sample, the law of averages typically assumes that unnatural short-term "balance" must occur."
Source:
http://en.wikipedia.org/wiki/Law_of_averages