Epstein said Rizzo felt soreness in the wrist after he swung and missed, but an X-ray taken Sunday came back clean.
After Rizzo was lifted for a pinch-hitter, speculation began that the hot-hitting 22-year-old first baseman -- who has a .354/.415/.713 slash line with 17 home runs and 46 RBIs in 48 games -- could be getting called up to the Majors.
The Iowa Cubs' official Twitter tweeted: "We have no further information on Rizzo. FWIW [For what it's worth]: All transactions involving Iowa Cubs players are always announced first in Chicago."
The affiliate's tweet turned out to be premature.
"It happens, I understand it," Epstein said. "It's part of the modern world. Things happen that didn't happen 10 years ago because of technology, and we all have to adjust."
Epstein and general manager Jed Hoyer reiterated Monday their plans to let Rizzo continue to develop in the Minor Leagues.
With the Cubs mired in a 12-game losing streak and 14th in the National League in runs entering Monday, fans have been hoping to see Rizzo's bat in the Major League lineup. Hoyer said he wouldn't put that kind of pressure on Rizzo.
Instead, Hoyer said it's up to the current Cubs to help snap the team's 12-game losing streak.
"No young player should ever be viewed as the savior or the changer of a struggling Major League offense," Hoyer said. "We have a lot of veterans on this team. We're going to get through this and get on the right track because of those veteran guys, not because of those young guys coming up through the Minor Leagues."