Moments ago Ken Rosenthal posted the following tweet:
Segura is a 22-year-old shortstop who just made his major league debut for the Angels on Tuesday. He was Baseball America's #55 prospect entering the season and was hitting .294/.346/.404 in 94 games for AA Arkansas this season.
I'll be updating this post as we learn more.
UPDATE (6:40 pm): Rosenthal confirms that the two pitchers involved are Johnny Hellweg and Ariel Pena. Hellweg is 23 and has a 3.38 ERA and 6.6 strikeouts per nine over 119.2 innings for AA Arkansas. Pena is a 23-year-old Dominican native who has a 2.99 ERA and 8.7 K/9, also for Arkansas.
John Sickels listed Segura, Hellweg and Pena as the Angels #3, 7 and 15 prospects in the Angels organization before the season. Segura was a B prospect, Hellweg a B- and Pena a C+.