McDonald arrived in time for batting practice Saturday at Busch Stadium. He has a career .246 batting average (175-for-711) with 38 doubles, five triples, 19 home runs and 78 RBIs in 306 big league games with Baltimore (2004), Minnesota ('07), Cincinnati ('09), Boston ('10-12) and the New York Yankees ('12).
The 34-year-old outfielder saw his most extensive Major League action with the Red Sox in 2010, when he batted .270 (86-for-319) with 18 doubles, nine homers and 34 RBIs in 117 games.
"Darnell's been swinging the bat really well lately," manager Dale Sveum said. "We'll give him a shot and see what happens."
Boscan, 33, was recalled from Triple-A Iowa on Thursday after Navarro injured his right ankle in a collision at home plate. Boscan did not appear in a game with the Cubs.
Carrie Muskat is a reporter for MLB.com. She writes a blog, Muskat Ramblings, and you can follow her on Twitter @CarrieMuskat. This story was not subject to the approval of Major League Baseball or its clubs.