Rizzo is now batting .344 (21-for-61) with five home runs and 15 RBIs off southpaws this season. He connected on his 13th home run with one out in the first, and his other two hits, both doubles, came off right-handers. It's quite a turnaround after last season when he batted .189 against left-handers, hitting seven home runs.
"I just feel very confident and that's everything in this game," Rizzo said. "I don't care what anyone says. Whether your mechanics are good or bad, if you're feeling confident at the plate, it makes a huge difference."
Tuesday marked Polanco's Major League debut, and Rizzo knows something about the expectations the outfielder will have to deal with. The Cubs first baseman played in his first big league game with the Padres nearly three years ago to the day, on June 9, 2011. He was sent down to the Minors after 35 games, and returned in September that year.
"I'm sure [the Pirates players] have been hearing nothing but what he's been doing in the Minors since April," Rizzo said of Polanco. "Now he's finally up here. I hope he does well. All of these guys get a lot of hype and it's not easy to just come into the big leagues and face Travis Wood throwing cutters.
"I can probably speak for [Polanco] and say he's never seen a left-handed cutter before in the Minors," Rizzo said. "It's a challenge up here."
Polanco did get a single off the Chicago starter, but that was on a fastball away. Did Wood throw the rookie a cutter or two?
"I threw him a couple," Wood said.
Was Rizzo right? Wood just smiled.
"He jams that ball inside, he changes speeds effectively," Pirates manager Clint Hurdle said of Wood. "We've seen it before. We had an opportunity to push on him in the fourth, in particular, and we didn't get that done. Other than that, he kept us away from the plate. We got on, but couldn't capitalize."
Polanco was the talk of Pittsburgh.
"He's a good looking young player," Chicago manager Rick Renteria said. "I thought his swing direction, his path direction is a little [Ken] Griffey-ish like. Time will tell where he's at."
The rookie could only stand and watch in the first as Rizzo's two-run homer sailed over him in right and nearly cleared the bleachers. Rizzo's blast drove in Junior Lake, who had singled with one out, and was his fifth off a left-hander. It was the 100th career home run off Liriano, and only the ninth by a lefty.
"He just left a pitch up," Rizzo said of Liriano. "I'm really trying to not do too much off him, and just keep riding the momentum off it. Every time I face a lefty, I feel it gets me back versus righties. That's how it's been in the past as well. I'm just keeping it simple."
This is the best he's felt against left-handed pitchers, at any level of his baseball career, he said.
"The tough lefties coming in late who are paid to get you out, somehow I'm getting knocks off them," Rizzo said. "I'm going to keep riding this momentum and keep going.
"It's a matter of not doing too much," he said. "I don't think I'll ever figure out lefties or righties. They'll make adjustments and I'll make adjustments."
The Pirates did, too, and tied the game with two outs in the third when Polanco singled for his first Major League hit, and Andrew McCutchen followed with his ninth home run and second in as many games.
Liriano couldn't finish Rizzo's second at-bat leading off the fourth. The Pirates starter threw three pitches, and had to leave the game because of discomfort in his left side. Rizzo greeted Jeanmar Gomez with a double and eventually scored on Darwin Barney's two-out double to take a 3-2 lead.
The Pirates loaded the bases with one out in the fourth and tied the game again on Josh Harrison's sacrifice fly.
With one out in the Chicago sixth, Starlin Castro walked and Justin Ruggiano was hit by a pitch for the second straight at-bat. Valbuena hit the first pitch into the gap in right-center field to go ahead, 5-3.
Rizzo added an RBI double in the seventh that Polanco had trouble catching up to. Rizzo then tallied on Castro's single for a 7-3 lead.
Although he has yet to appear in the top five in the National League balloting, the Cubs could make a case for Rizzo to be their All-Star representative on July 15.
"The first basemen in this league, they're all All-Stars," Rizzo said. "I'll just keep playing my game and not let it affect me."