The 23-year-old is expected to get much of the playing time at first base the rest of the season, while the Nationals take a look at him and move Michael Morse back to left field, where he'll likely end up next season. It's unlikely Marrero starts next season at first base - Adam LaRoche should be back, and there's no telling what will happen if players like Prince Fielder and Albert Pujols hit the open market - but if LaRoche is the starter, it's not impossible that he gets traded and Marrero supplants him midway through the season.
For Marrero, the call-up comes after a long journey through the minor leagues that's spanned three positions, four levels of the minor leagues and included a nasty injury when Marrero broke his leg sliding into home in 2008. He reported to camp this spring looking leaner and stronger than he had before, after working with a nutritionist in the offseason and cleaning up his diet. He showed softer hands and a more nimble frame at first base than he had in previous springs, and followed it up with an impressive season at Triple-A Syracuse, hitting .300/.375/.449 with 14 homers, 69 RBIs and only five errors at first base.
With a full month in the majors, Marrero has a chance to make things interesting in 2012. He'll get to start his time in the majors tonight in Cincinnati.