Siemens, who was an 18th round selection by the Diamondbacks in last year's Major League Baseball Amateur Draft, has been with the South Bend Silver Hawks in the Midwest League. While in South Bend, Siemens made 16 appearances (2 starts), going 4-1 with a 4.14 ERA.
In 37 innings, he had 30 strikeouts and just 10 walks while opponents hit .260 against him.
Over the course of his last 10 appearances, he was 4-1 with a 3.42 ERA, striking out 21 in 26.1 innings. He didn't allow a run in five of those outings. In his first start of the season, Siemens allowed just one hit in five scoreless innings with four strikeouts against Quad Cities on May 1.
Visalia is currently 28-33 in the California League-North Division. The Rawhide are scheduled to play the Inland Empire 66ers July 7-9 in San Bernardino.
Siemens played at CBU from 2009-11, earning GSAC Pitcher of the Year honors in 2011 while leading the Lancers to their second straight conference title and national tournament appearance. He is CBU's career leader with 26 victories, second with 245 strikeouts and fourth with a 3.02 ERA.