The move has been anticipated in Reds camp after the club learned that closer Ryan Madson would need season-ending surgery to repair a torn ligament in his elbow. The other option would have been a closer-by-committee set up.
"It's Marshall right now," Baker said after the game, adding he's been impressed with Marshall's spring.
In 10 appearances, Marshall has a 3.27 ERA and has held opposing hitters to just .179 at the plate. Marshall struck out 16 batters in 11 innings this spring, while walking three. He is slated to pitch again Tuesday in the the club's Futures Game at Great American Ballpark.
It will be the first time Marshall has been designated as the closer. In six seasons with the Cubs, he had seven saves while posting a 3.96 ERA. He made 78 appearances last season and notched a 2.26 ERA, the lowest of his career.
"He can throw that breaking ball any time, which is tough to do in Arizona with this light air here," Baker said. "He's basically unfazed by situations and things. He's been around a while and he's a veteran guy that's had good success."