Rizzo, who did not play Wednesday after bruising his right knee on Tuesday, was batting .367 and leads the Pacific Coast League with 22 home runs. He's hit four homers in his last three games.
Sveum and Theo Epstein, the Cubs president of baseball operations, have talked about the highly touted first baseman often.
"We haven't come up with any set time yet [to call him up]," Sveum said Wednesday. "Obviously, we've talked about it. Still, we haven't come up with that set date."
It's hard to ignore his offensive numbers, especially when the big league team is struggling.
"His name is brought up pretty much every day," Sveum said. "He's that guy -- you get your email and look at the Minor League report right away to see if he hit another home run, which he's done quite a bit lately."
Rizzo hurt his knee sliding into a fence in front of the visitor's dugout in Des Moines chasing a popup. He was listed as day to day.