Von Rosenberg is traveling to Pittsburgh, where he will undergo a physical on Monday. The signing will then be officially completed and announced after that takes place.
"There is nothing official, but we are optimistic that we can get something done with Zach," general manager Neal Huntington said on Sunday. "He would be a great addition to this farm system."
Once the signing is official, it will complete the Pirates' lofty goal of luring three high-ceiling high school arms away from college commitments by offering significantly above-slot signing bonuses. Zackry Dodson (fourth round) and Colton Cain (eighth round) were the other two in the trio and came to agreements with the organization on Friday. Both have since begun training in the Pirates' Bradenton, Fla., facility. Cain signed for a $1.15 million bonus, while Dodson's was reported by Baseball America to be worth $600,000.
"The ability to diversify our investments this year is really going to pay off long-term," said Huntington, who had the available funds to offer high signing bonuses later in the Draft because of the Pirates' ability to sign first-round pick Tony Sanchez at slot. "Obviously it will play itself out in five to seven years whether our Draft picks were the right ones. We feel very good about the process of how we got here today."
Von Rosenberg, a right-hander out of Zachary (La.) High School, had a verbal commitment to Louisiana State University and dropped to the sixth round of the Draft because of his perceived intention to honor that commitment. He was on hand to watch the Tigers claim a College World Series championship in Omaha, Neb., in June.
The 6-foot-5 pitcher was on a state championship high school team in each of his four years. He went 11-1 as a senior and was named the Gatorade Louisiana Baseball Player of the Year. He also hit .489 with 10 home runs and 45 RBIs last season.
Signing Von Rosenberg will bring the Pirates' total of Draft picks signed to 21 of 51, and will ensure that the club has signed each of its first nine selections. The Pirates still have approximately $2 million remaining in their predetermined Draft budget and continue to pursue additional players in advance of the Aug. 17 midnight signing deadline.
"We're not done," Huntington said. "We've still got a few ongoing conversations with a couple players to see if there is common ground between their asking and our value on them. We're very pleased with where we are at this time. We'd just like to add one or two or three more."
Jenifer Langosch is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.