Mengden, who is ranked No. 14 among Oakland prospects, has absolutely dominated at the Minor League level this season, posting a combined 1.19 ERA in 11 starts between Double-A Midland and Triple-A Nashville with 67 strikeouts in 68 1/3 innings.
In seven starts for Nashville, Mengden has limited opponents to seven earned runs in 45 1/3 innings.
The 23-year-old, originally a fourth-round Draft pick by the Astros in 2014, was acquired by the A's last summer in the Scott Kazmir deal.
Jane Lee has covered the A's for MLB.com since 2010. This story was not subject to the approval of Major League Baseball or its clubs.