Borchering, who was selected No. 16 overall in June's First-Year Player Draft, was one of the D-backs' two first-round picks. The other, Notre Dame outfielder A.J. Pollock, was taken at No. 17 and signed not long after the Draft.
Borchering, who took batting practice with the D-backs on Friday, received a $1.8 million signing bonus and will leave for Rookie League Missoula on Saturday.
"I've never been to Montana," Borchering said. "But I'm looking forward to it."
Borchering took some good-natured ribbing from D-backs players while he hit.
"Walking out onto the field was an experience I'll never forget," he said. "Looking out it just seemed so surreal, like all my dreams had come true. It's something I'm never going to forget. I'm so proud and honored to be part of this organization, it's something I've been working a long time for and I'm really excited to get out and start playing."
A switch-hitter with power from both sides of the plate, Borchering played third base in high school, and while some scouts see his future at first base, the D-backs will start him off at third and D-backs scouting director Tom Allison said he envisions Borchering sticking at the position.
That certainly seems to be Borchering's plan as well.
"Everybody has their opinions, but I take that and I like to use it for motivation," Borchering said of the talk he would have to move to first. "This summer I've been working a lot on defense, and I think I've made some good strides. I'm going to battle for third base because I really love the position and I think I can be a plus defender there."
The 18-year-old out of Bishop Verot (Fla.) High School is listed at 6-foot-4 and 200 pounds. As a senior, he hit .494 with 13 home runs. He has been likened to Atlanta Braves star third baseman Chipper Jones and was named the Gatorade Florida Baseball Player of the Year.
The D-backs had hoped to get Borchering signed earlier in the process -- Monday is the deadline for players to sign -- but with Borchering having committed to play at the University of Florida he had some leverage and the D-backs wound up going over the slot recommendation to get him signed.
"Negotiations are always tenuous at times, but everybody wanted the same thing and that was for Bobby to start his professional career now and we're very excited it came to this point," Allison said. "We go to ownership with our budget and they allow us to select players that we feel are going to be players for the Arizona Diamondbacks and we were able to negotiate the contract fit with what the Arizona Diamondbacks were willing to do."
"It was a hard one because I really like the University of Florida," Borchering said of his decision.
With the Borchering signing, the one lone pick of note that remains unsigned is infielder Matthew Helm from Hamilton (Ariz.) High School. Helm slipped to the seventh round after a pair of injuries caused him to miss time.
"We're grinding away," Allison said. "We want him to be an Arizona Diamondback."
Steve Gilbert is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.