Here's my writeup on Herrig/Casey:
Both Herrig and Casey seem to have grown by leaps and bounds since their UFC beginnings. While Herrig technically won her UFC debut, she has a TUF loss to Randa Markos and a loss to Tecia Torres in Invicta. After her loss to VanZant, people were writing her off as occupying the very bottom of the women's strawweight barrel as she closed as a underdog to perennial loser Kailin Curran.
Herrig has been pretty vocal about how combined health and mental issues have prevented her from performing. The list includes hormonal issues, gastrointestinal imbalances, nutritional deficiencies, anxiety, depression, and fatigue. Having addressed those issues, she promised that we would see a much better Herrig coming into the Curran fight and moving forward. Apparently, these changes made a difference as she steamrolled Curran, and won her next two fights against the heavily favored Grasso and slightly favored Kish.
Against Grasso, Herrig showed off improved striking and a good sense for winning rounds. Though being significantly overpowered, she thoroughly outgrappled and nearly finished Kish, literally making Kish shit her pants (which under many athletic commissions would've been scored a TKO victory and would've cashed my Herrig ITD bet).
Though starting her MMA career as a former kickboxer, she has only one TKO victory back in 2011. Without significant power, her striking is designed to score points. Not particularly strong for her division, Herrig has worked hard to improve her technical grappling and jiu jitsu skills.
Casey also had a rough going early in the UFC. Nobody faults her for losing after flying in on short notice to the UK to fight JoJo Calderwood. She also dropped her next fight to atomweight
Seo Hee Ham in Korea. Only in her 3rd fight on home soil against euro debutante Cristina Stanciu was she able to pick up a win (Santicu would be dropped by the UFC soon after). After submitting Randa Markos by armbar only one month later, the UFC matched Casey up with #1 contender Claudia Gadelha. Too much too soon because she soundly lost that fight.
The fight with Gadelha also exposed some of Casey's weaknesses. At a significant wrestling disadvantage, Gadelha landed takedowns at will. One can make excuses for Casey getting tossed to the mat against one of the best TD artists in the division. However, she ended up on her back multiple times against both Jojo Caldwerood in her debut and against Jessica Aguilar 2 years and 5 fights later.
A lot of this propensity to get dumped on the ground is due to her striking style. In many of her fights, the action starts the same way: Casey blitzing forward with a 4 or 5 punch combination. It's become her MO in fights to blitz her opponent like this. The result has been that she has scored points when these combos land, but also it results in her running into a level change and being easily taken down. Calderwood and Aguilar didn't have to shoot doubles like Gadelha, Casey would just rush into them resulting in a relatively easy throw to the ground.
Although being on her back multiple times in fights (often in the same round), most of her opponents have been wary of her guard and upkicks. Calderwood and Gadelha let her up over and over. Aguilar's strategy was to lean forward and eat Casey's accurate upkicks. When she did get Casey to the ground and attempted to control her early in the fight, it seemed like Casey had a hard time getting back up (luckily for Casey the ref stood them up).
Casey is the more athletic and dynamic fighter, but she doesn't seem to have a gameplan as to how to win rounds against her opponents. She fights them all the same way: rush forward, be aggressive, and throw a lot. This along with her willingness to go to the ground will make it tough for her to beat Herrig.
Herrig's path to victory should be the same as the one she employed against Kish. And her corner's advice between the 2nd and 3rd rounds will apply to this fight as well. To paraphrase: "Take her down. Stay on top. Don't worry about being boring just win the fight." Although Casey may be better off her back technically than Kish, she also isn't as strong or explosive, and won't be able to power out bad positions. Although Casey will have her moments, Herrig always has the option to take it to the mat and be in control. Casey is too willing to let her opponents dictate the action, and Herrig has the fight IQ to do just enough on the ground to win rounds.
-140 Herrig may have some value. Although she likely wins by decision, there's a chance she can lock in a sub again, so the ML looks like a safer bet. For those looking for a hedge, Casey DEC +297. Herrig has technically never been stopped in her pro career (although she did tap to an armbar against Markos in TUF). Herrig is also much better grappler now.