The Rays signed Shaffer, the team's first-round pick and the No. 25 overall selection in last month's First-Year Player Draft, on Friday. The 21-year-old third baseman will report to short-season Class A Hudson Valley on Saturday.
Shaffer batted .336 with 10 homers and 46 RBIs in his final season at Clemson, and he was ranked as the 16th overall prospect heading into the Draft by MLB.com.
"We knew all along something was going to get done," Shaffer said. "But you have to go through the whole process. I'm just really excited about being here right now. This is a dream come true. I get antsy watching batting practice and not getting to swing. I'm just excited to be here right now. This is incredible and I'm just excited to get going."
MLB.com has confirmed the Rays have signed Shaffer for $1,712,500, which is just shy of the assigned value for the pick, $1,725,000.
Under the new collective bargaining agreement, the deadline for teams to sign their Draft picks is 5 p.m. ET on Friday. The Rays have now signed their top 28 selections and 37 of their 40 picks overall.
In years past, the signing deadline fell in mid-August, which often led to the drafted player losing the opportunity to play during the summer if he waited until the deadline to sign.
"I like the early deadline because I get to go out and play," Shaffer said. "... We all got it worked out. I'm happy, they're happy and I'm ready to go."
After spending the first two seasons of his collegiate career at first base, the 6-foot-3, 210-pound Shaffer moved to third base for his junior year. As for where he plays with the Rays, Shaffer said that will come down to whatever helps him progress quickest through the organization.
Rays executive vice president of baseball operations Andrew Friedman said he expects that progression to be smooth.
"He's one of those guys who has a chance to get here relatively quickly," Friedman said after the Draft. "We never move guys too quickly, but on a relative scale, pretty quickly."
Shaffer views "getting used to the everyday grind" as the biggest challenge he faces.
"Playing every day and just the mental ups and downs," Shaffer said. "Obviously the talent gets better every time you move up in an organization. But it's still the same game ... it's more on the mental side. Just handling adversity and just handling the grind of Major League baseball."
When asked if he had a goal for when he might reach the Major Leagues, Shaffer smiled.
"I'd like to be playing tonight," Shaffer said. "But that's not something that's very realistic."
Kidding aside, Shaffer sounded ready to get to work.
"I can't put it into cruise control now," he said. "I mean I've got to work as hard, and harder than I ever have before. These are the best players in the entire world playing at this level. This is just the very beginning and I just scratched the surface and I plan on working as hard as I can."
Bill Chastain is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.