D-backs No. 1 prospect Archie Bradley started for Mobile. He allowed one run on four hits and four walks in 4 1/3 innings. He struck out three batters and threw 98 pitches.
In eight starts with Mobile since returning in June from a strained flexor mass in his right elbow, Bradley is 2-1 with a 3.76 ERA. He has struck out 31 batters and walked 23 in 38 1/3 innings.
O'Brien began the season with Class A Advanced Tampa and earned a promotion to Double-A Trenton in May. Between the two levels he was hitting .267/.314/.588 with 33 homers and 71 RBIs when he was traded. He ranks third in the Minor Leagues in home runs, trailing only Rangers No. 1 prospect Joey Gallo (37) and Cubs No. 1 prospect Kris Bryant (36).
While O'Brien has broken out at the plate this season, he has yet to find a home defensively. He was a catcher in college, but has split his time at catcher, first base and in the outfield this season. After catching his first two games with Mobile, he played right field Monday.
Teddy Cahill is a reporter for MLB.com. Follow him on Twitter at @tedcahill. This story was not subject to the approval of Major League Baseball or its clubs.