Ellis, who played third base last year for University of Louisville, also tweeted out a picture of himself signing his contract with the D-backs.
"We spent a lot of time, we had a tremendous amount of looks throughout the course of the year," D-backs scouting director Deric Ladnier said after the team selected Ellis. "Then he really continued to grow as a hitter. The power was very evident. His ability to use the whole field was evident. It's just a very easy, professional stroke."
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Ellis has a quick, compact swing and uses the leverage he has in his 6-foot-3 frame. He has shown a good feel for the strike zone as well, walking 38 times and striking out the same number.
"He just has this tremendous knack to find the barrel to the ball," Ladnier said.
Also Tuesday, the D-backs agreed to a deal with fifth-round pick Buddy Kennedy, a third baseman out of Millville (N.J.) High School, according to MLB.com's Jonathan Mayo. Kennedy, who is friends with Angels outfielder Mike Trout, signed for $550,000, which was above the slot for the pick of $356,900.
Steve Gilbert has covered the D-backs for MLB.com since 2001. Follow him on Twitter @SteveGilbertMLB. This story was not subject to the approval of Major League Baseball or its clubs.