I'm going to go against the flow and say that there are quite a lot of 'mediocre' brown belts who would have a hard time at blue belt level. I honestly doubt that I would win the worlds at blue light if I entered it this year. There are over 100 people in that division, and each fight is six minutes. Even leaving aside the wrestlers, anyone can have one really good sweep that works, or hit a nice takedown at the beginning, and stall out someone if their conditioning is solid and they know how to play a safe game. Heck, there are blue belts out there who have been training longer than some browns, or at least in the four or five year times, as well as the ones who started when they were really young.
Example, Roberto Satoshi - fought the Brazilian Nationals at Green Belt in 2002. At 13. So his first Blue Belt Adult competition would have been, say, four years later. By that stage, he's got probably seven years training, he's strong, he's fit, and he's a serious competitor. And this is the norm for a lot of the bjj prodigies who started young. You honestly expect a guy who has come two or three times a week for seven or eight years, at forty years old, to handle a guy who has been training full time for seven years?
So...I've said this before, but several of the Purples at the Worlds could have potentially placed at Brown. And I have no doubt that the best blues could beat the worst browns at the worlds. All the time? Perhaps not. But it's very much within the realm of possibility.
Who was the Blue Belt who beat a Black Belt in Gi at the Fila Worlds Grappling?
Just saying it's possible. Heck, we have a blue belt here who's tapping browns, and he's been training for just over a year and a half. And he's a light featherweight.
[Edit: Oh, and he fought the Worlds this year at Blue, and lost in the quarters to the guy who won. So he didn't even medal.]
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