Rizzo won't officially be promoted until Tuesday. The Chicago Tribune reported Rizzo was removed from the Iowa Cubs' Monday game in the fourth inning and will arrive in Chicago later Monday.
The slugging first baseman was hitting .345 with 23 home runs, 62 RBIs and 18 doubles in 69 games entering play Monday.
He anticipated debut isn't the first stint in the big leagues for the 22-year-old. He hit just .141 for the Padres in 153 plate appearances after dominating Triple-A pitching.
Getting production from the middle of the order has been a problem all year for the Chicago Cubs.
The Cubs wanted to avoid calling Rizzo up in position to be viewed as a savior, but the team's struggles and Rizzo's excellent first half left them almost no choice.
"Our core guys have got to start doing something in the middle of the order," manager Dale Sveum said Sunday, before the Rizzo transaction was confirmed by the team.
"We've talked about it," Sveum said. "But it always would be nice to have somebody hitting behind him, too. Whenever you have somebody with that much hype and that much ability, it always helps to at least have somebody hitting behind him."
The Cubs have had trouble hitting with men in scoring position. The trick for Sveum becomes how to arrange the middle of his batting order. Rizzo and first baseman-outfielder Bryan LaHair bat left-handed, and left fielder Alfonso Soriano hits right-handed.