Corniell will undergo season-ending surgery to repair the UCL in his right elbow, Evan Grant of the Dallas Morning News reports.
Corniell will open the season on the injured list at Double-A Frisco with elbow inflammation, Jim Callis of MLB.com reports.
The Rangers optioned Corniell to Double-A Frisco on Sunday, Jeff Wilson of RangersToday.com reports.
The Rangers selected Corniell to their 40-man roster Tuesday.
Corniell struck out six and gave up one earned run on three hits and one walk in four innings Tuesday in his first start for High-A Hickory.
Corniell has a 3.80 ERA, 0.97 WHIP and 28 strikeouts in 23.2 innings for Single-A Down East.