She's not on the official roster (linked above), which basically confirms the rumors floated around on other sites (namely PowerMizzou) earlier today. Erwin was in a battle with Nicole Hudson for the role of Chelsea Thomas' Primary Backup, and she wasn't doing tremendously well in that effort so far this year.
I guess that makes Nicole Hudson the official No. 2 pitcher, with perhaps senior Lindsey Muller (who pitched a decent amount in 2011) the stopgap No. 3? Regardless, this is a blow to Mizzou's depth, especially considering all we've heard about Ehren Earleywine wanting to protect Thomas' arm for May. Plus, since Thomas, Hudson and Muller are all seniors, that means Mizzou will be leaning heavily on two stud freshmen -- Maryland's Tori Finucane and Idaho's Casey Stangel -- in 2014.