Mariners general manager Jack Zdurienick's second trade of the day was for a 26-year-old pitcher with three games of major league experience as a reliever -- all in the last three weeks. Manuel has just 40 games of experience above Double-A.
Seattle designated Balentien for assignment on Sunday. The 25-year-old had struggled as Seattle's left fielder following a season-ending injury to Endy Chavez, hitting .213 with 13 RBIs in 56 games.
Balentien was at his home in Arizona after being designated for assignment. The Reds expect him to join the team before the start of a series against Colorado on Friday.
Manager Dusty Baker said he'll work him into the lineup slowly.
"He's strong," Baker said. "He's a little bit rough. He hadn't played that much lately. He has some tools. He hasn't played in a while, so I might take a few days to get him in the lineup."
Balentien got his first substantial time in the majors last year with Seattle and batted .201 with seven homers and 24 RBIs. He doesn't draw many walks or steal many bases.