After being drafted by the Cubs, Day went to play in the Cape Cod League with the Harwich Mariners and batted .243 in 40 games this summer.
Despite being drafted in the middle rounds, Day was asking for a signing bonus equivalent to that of top-five-round money.
A left-handed hitter that has also taken reps in the outfield, Day injured his hamstring early on in the season with Michigan State this past year.
He said Wednesday that his talks with the Cubs went well, but that he was told by the team that they could only offer a certain dollar figure.
"They followed me all summer," Day said of the Cubs. "They liked what they saw, but couldn't come up with the money I was asking for.
"We got pretty close and had some good conversations, but they (said they) just didn't have too much money left to give me," said Day, adding, "They'd love to have me, but where I was taken there wasn't much of a priority.
"If they could have gotten me for a steal, they would have," he said.
Wednesday is the final day to sign all players from the 2007 draft class with the exception of college seniors. Day, along with first-round pick 3B Josh Vitters and INF Victor Sanchez (their 25th-round pick) are the Cubs' three highest drafted players that have not signed with the organization.
Cubs Scouting Director Tim Wilken told InsideTheIvy.com earlier this month that talks between the club and Vitters had gone well.
"All of our talks and meetings have been pleasant. There's nothing that's been alarming or negative. Everything has been positive," Wilken had said.
The Cubs have until midnight to sign Vitters, who batted .390 with nine home runs in 24 games for Cypress (Calif.) High School this past season.
A versatile infielder throughout his prep career at Gahr (Calif.) High School, Sanchez committed to the University of San Diego and has spent his summer in the Northwoods League with the Alexandria Beetles.
Sanchez first told InsideTheIvy.com back in June that his plan all along was to head to college and San Diego for three years.
"I was surprised when they drafted me," Sanchez had said of the Cubs. He later said that he would sign if the club offered the right amount of money.
A member of the USA Junior National Team in 2006, Sanchez batted .275 with eight doubles in 42 games this summer with Alexandria.