Vitor is a guy who is very hot & cold. On a good day, he might beat any MW on the planet, almost any LHW on the planet (on his best days). At other times, he's been known to underperform, give up (sometimes shows a lack of "heart"), etc. I consider GSP the all time GOAT, yet he lost to a guy who spent most of his career at LW (Serra), but GSP also beat some all time greats. In MMA, it is almost impossible to be undefeated. GSP lost to Serra fair & square the 1st time, it's the nature of MMA, shit happens. If they fought 5 times, GSP wins 4 out of 5, that night happened to be the 1 time for Serra. Hughes lost to There are too many variables & ways to lose in MMA. Rampage was very good but not yet in his best peak form, & styles make fights. Hughes is another all time great WW, 1st time he lost to Hallman people said it was because he was a noob. In their rematch, Hughes had a record of 22 - 1, yet he still lost to Hallman again. No one would try to argue Hallman had a better career than Hughes or that he is a better fighter than Hughes, styles make fights & sometimes a guy just has your number.
Prime Saku was a legit candidate for #1 P4P at the time (not in today's MMA rankings, for the rankings at that period in time). I'm not saying he was the #1 P4P, just that he warranted discussion as a legit candidate at some points during that period. He's really a WW by modern MMA standards, who fought some of the best at heavier weights, & even beat some of them.