/Prepares to make up an excuse how Clare got faster to satisfy shinta:

Image ripped from the manga because the anime clouds her legs in snow and dust to avoid drawing them. All scenes shown have already appeared in the anime.

Take a full look at Clare's new legs, and compare them to Rigardo's


Rigardo has fairly normal looking legs (maybe a little hairy since he's a lion-man now). The speed in his legs is the same as any other part in his body. He's just freaking fast. Clare's legs are all freakish tendons and are counterbalanced to keep her upright. Hoofed feet, which further explains her lack of ability to control them at first. Her legs were twisted into this form with only one thought in her mind, speed.

Let me tie in a different aspect. Ophelia gave us a full explanation on how Claymore becomes either an Offensive, or Defensive warrior. This was alluded to again recently with the discussion between Deneve and Undine. Clare thought of only killing Priscilla when she became a Claymore, and now she's Offensive.

Here, Clare thought of only being faster than Rigardo in order to save Miria as she allowed herself to awaken. The form her legs appeared in is superior to Rigardo's in terms of speed. It's so fast that it is well beyond her, so she uses her claymore and her hands to force some semblance of control into them as she got used to it. Even Rigardo realized that she'd never touch him as long as he was able to move.

Rigardo was never really serious with Clare (or any of the Claymores) until the end of their bout. That resulted in being handicapped when she sliced off his arm. He probably would have killed her easily if she hadn't. By that time, Clare had gotten used to the new legs, was now far faster than he was due to the form her legs twisted into.

Lastly, yoki does not equal speed. Yoki is the fuel that all Claymores and Awakened Beings tap into to feed their abilities. Miria uses hers in short bursts that equaled Rigardo until she got tired. Clare has done the same with the Flash Sword. Flora recognized that her Windcutter wasn't faster than Clare's Flash Sword with Irene's arm. There exists a possibility that Clare could cut Miria in half before she vanished (assuming they were standing still at first and Clare got to swing first). The speed is a combination of physical abilities powered by Yoki. Strength isn't speed.

Clare is lighter in mass than Rigardo. By a lot. Her legs in a form meant only for speed, her lighter frame moves faster than Rigardo's.

(There. Totally made up with various assumptions based off things we've blatantly been told and "screencaps")