"He's definitely an interesting player," he said.
Castillo, 5-foot-9, 200 pounds, participated in live batting practice, threw from the outfield and fielded grounders at shortstop in front of representatives from 28 of 30 teams at the University of Miami. He's known for his speed and athleticism and likely will start the season in the Minor Leagues when he signs, but there's a belief that he could be in the big leagues by the end of this season and compete for a starting job next Spring Training.
Castillo, who left Cuba six months ago, established residency in Haiti and was cleared by the U.S. government to sign with a team earlier this month. He is represented by Roc Nation Sports, a joint venture between Roc Nation and CAA Sports.
"An international free agent who does not count toward the pool allotment is going to be sought after," Luhnow said. "The recent success of some of the higher-profile Cuban players -- [Yoenis] Cespedes, [Yasiel] Puig, [Jose] Abreu -- put this guy in a pretty good spot. He's a little different player from those guys, but he'll have a good market. We'll expect it to be competitive."
The Astros made a strong run at Abreu, and earlier this year offered Japanese pitcher Masahiro Tanaka a contract of at least $100 million.
"Eventually, we'll get our guy," Luhnow said. "We're doing it to sign guys, but we want to make sure we do it in a responsible way."
Brian McTaggart is reporter for MLB.com and writes an MLBlog, Tag's Lines. Follow @brianmctaggart on Twitter. This story was not subject to the approval of Major League Baseball or its clubs.