The Cubs' top prospect tied a team record by scoring five runs, part of a three-hit, three-RBI afternoon Tuesday, as Triple-A Iowa pounded the visiting Tacoma Rainiers, 18-8.
Rizzo tied the mark set most recently by Roosevelt Brown on Aug. 15, 1999.
"That's a record for me," he told the Des Moines Register. "I've never done that before. Never."
The 22-year-old first baseman started his record-setting day with a leadoff homer, his Pacific Coast League-leading 15th, in the second inning. An inning later, he reached on an error and came home on a throwing error as Iowa scored six times to build a 7-1 lead.
In the fourth, Rizzo reached on another throwing error -- Tacoma committed a PCL season-high seven miscues -- and trotted home on a base hit by No. 11 prospect Josh Vitters. MLB.com's No. 33 overall prospect also was in the middle of the I-Cubs' five-run fifth, delivering a two-RBI single and scoring on Luis Valbuena's double.
Rizzo eclipsed his previous career high and tied the club record in the seventh when he singled with one out and scored on Dave Sappelt's two-run double.
"Long day," he told the newspaper.
Even the parent club admits there's little left for Rizzo to prove at Triple-A. He's eighth in the PCL with a .352 batting average and leads in homers, RBIs (39), slugging percentage (.692) and total bases (108).
Asked over the weekend about a possible promotion for the 2007 sixth-round Draft pick, Cubs manager Dale Sveum told MLB.com, "That's definitely going to be talked about. He's done everything he can down there, but once again, when you bring somebody up like that, he has to play every day. That's the million-dollar question. How do we get that playing time?"
First baseman Bryan LaHair has been Chicago's best offensive player, hitting .315 with 10 homers and 21 RBIs in 39 games. If Rizzo is thrown into the mix at Wrigley Field, one of them would have to move to the outfield.
"I'm competitive and athletic enough to believe that I could play in the outfield," Rizzo told the Des Moines Register. "I would love to play center field and shortstop, but that's obviously not going to happen.
"My focus is on first base. Over the years, I've grown into a routine. Taking ground balls is a way of life."
Valbuena also had a big day for Iowa, contributing a homer and four RBIs and falling a triple shy of the cycle. The Cubs totaled 18 hits in support of Chris Volstad (1-0), who allowed four runs on seven hits over six innings in his first start since he was assigned to Triple-A on Friday.