San Francisco now has signed 14 of its first 19 selections, though Gillaspie is the only signee among the club's top four picks. Director of player personnel Bobby Evans wouldn't disclose the terms of the deal, per team policy, but he said the signing process was "typical" and had been "ongoing since the day we chose him."
On Monday, a Wichita, Kan.-based NBC news affiliate reported Gillaspie had agreed to a pro contract with the Giants that included a $975,000 signing bonus and other incentives.
Of the 16 players chosen in the supplemental round, Gillaspie was the second to last to sign a deal.
The Giants have yet to ink their first, third and fourth-round Draft picks, but Evans said "our schedule is wide open all the time" to negotiate.
As to why some selections hadn't been signed yet, Evans said, "When players first go through the Draft, they have expectations as to what they'll get depending on where they're chosen."
The 37th overall selection, Gillaspie earned All-America honors last year while leading Wichita State to an NCAA Super Regional appearance. He batted .419 with 16 doubles and 11 home runs, and was named Cape Cod League Most Valuable Player in 2007.
David Biderman is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.