Yesterday was the debut of Ronda Rousey, Olympic bronze medallist, in the UFC. It was also the most attention in recent memory focused on a MMA fighter with a distinctively judo style, and I think it warrants a /r/judo community discussion and analysis of Rousey's toughest challenge to date. Please chime in with any comments or analyses of your own! It should be interesting and educational.
The match starts off by Rousey trying to jab her way into a clinch, and Carmouche presumably trying to implement her game plan by breaking off the clinch and moving away. However, the forward pressure of Rousey backs Carmouche into the cage and allows a stronger clinch and headlock by Rousey, albeit by eating a couple of hooks.
Against the cage, Rousey puts her lead left leg in between Carmouche's legs, and pulls Carmouche's head forward. What I believe was Rousey's plan at this point was to do exactly what she did to every other fighter she has dominated in the standing game: a basic combination attack of a forward throw (e.g. koshi guruma, hip wheel) and a backwards leg technique (e.g. ouchi gari, major inside reap). Carmouche, to my eye, seems prepared for this kind of clinch fighting as she resists a low commitment kouchi gari (minor inside reap) at -4:40 and a probing uchimata (inner thigh throw) at -4:37. However, Rousey manages to do a weak koshi guruma at -4:35 and the fight is now on the ground.
What I think Carmouche could have done better in this sequence was to recognise that she could have potentially countered Rousey backwards. Specifically when Carmouche was dropping her weight, pulling her hips back, and trying to pull her head out of Rousey's headlock, that momentum could have been used to drag the fight down into a position favourable to her (e.g. tani otoshi, valley drop). From what I've seen of Carmouche, her best work is "ground and pound" from top position. Instead, her instinct to pull her head and hips out and stay that way for a prolonged period broke her balance, and allowed Rousey to wrench her down with koshi guruma. Carmouche did better than any other opponent of Rousey in maintaining her balance, but she still made a mistake.
The koshi guruma lands straight into hon kesa gatame (basic "scarf" hold) with Rousey on top, and then quickly into makura kesa gatame (pillow "scarf" hold). There's already been some discussion about what happened here, so I'll probably be repeating some things I've opined about. Carmouche walks on the wall and does use it as leverage later for a back take. However, I believe the large part of why Rousey had her back taken was because she sacrificed her pin security for an attempt at a leg-entanglement armlock variation (ude hishigi ashi gatame) from kesa gatame at -4:25. In trying for the submission, she momentarily gave up secure arm control by feeding Carmouche's arm to her right leg. Another consequence of trying for ashi gatame was that Rousey narrowed her kesa gatame leg base, making the pin more susceptible to reversals. Carmouche showed excellent awareness of Rousey's vulnerability by kicking off the wall and taking Rousey's back at -4:22.