Hamilton, 22, batted .174 (4-for-23) with two triples and nine strikeouts. He was in camp as a non-roster player.
"He hasn't been switch-hitting that long. His record here in Spring Training, he's not doing real well for a guy that has speed," Reds manager Dusty Baker said before the move was revealed. "He's striking out too much. He had to come here to see where his development is, where he is, and realize he has some ways to go. If he didn't, he'd be here already."
Hamilton, who stole a professional-record 155 bases last season at Class A Bakersfield and Double-A Pensacola, has been learning a new position after switching from shortstop in the offseason. With his prowess for stealing, the organization felt his body would take less of a beating in the outfield.
During the eighth inning of Monday's 4-3 win over the Rockies, Hamilton's blazing speed was on full display as he hit a triple to the gap in right-center field. Had Tyler Colvin not cut it off quickly, Hamilton might have had an inside-the-park home run.
"He was really flying," Baker said. "We're enamored by speed because there's less of it around. When I was playing, if you couldn't run, you better be able to hit a bunch of home runs because most guys could run."
Hamilton being cut comes as no surprise. The expectations entering camp were that he would begin the season at Triple-A Louisville.
Hayes was 0-1 with a 3.86 ERA in six spring relief appearances. There are 37 players remaining on the spring roster.
Mark Sheldon is a reporter for MLB.com. Read his blog, Mark My Word, and follow him on Twitter @m_sheldon. This story was not subject to the approval of Major League Baseball or its clubs.