The main thing is that he hasn't been able to show a great speed advantage in either of those fights, but he has at middleweight and that has been the main key to his success.
This is flat out wrong. He looked fast compared to old, retiring fighters. Arguably he looked fast next to Weidman, who is fairly slow and nearing the end of his career himself. Because Kelvin is undersized, however, Weidman still took him down and choked him out.
Woodley is absurdly faster than middleweights and Kelvin looked just fine, competing with the second most accomplished welterweight of all time and the top of this generation.
The Weidman fight is the only fight that he was out grappled and finished.
This is a silly way of saying "literally the only wrestler he faced at middleweight."
Weidman is the biggest and best offensive wrestler/grappler in the division (Yoel rarely uses his wrestling).
This is demonstrably wrong.
Kelvin did not have the same problems with Jacare or Kennedy, who are both big skilled middleweight grapplers.
Kennedy had not fought in TWO YEARS, and retired immediately after his fight with Kelvin. Verbatim, he said he didn't have the physical capability of competing anymore at that level.
Jacare is nearly 40, well outside his prime, and it still went to a gritty razor thin controversial decision.
...
Kelvin is woefully undersized at middleweight, which is why he can only beat old farts. He can win some against mid-tier guys, but you are going to watch him get his face horrifically punched in like we did last weekend or choked out like he did with Weidman if he sticks around fighting his peers.
He's a special talent, so good he can just hang in there in a division he doesn't have the size for.