Rizzo crushed the first pitch he saw from Marlins right-hander Kevin Slowey into the right-field stands for his fourth homer in his last six games.
With consecutive game-winning hits -- following Thursday's solo homer against the Mets -- one would think Rizzo's confidence is booming. The 24-year-old acknowledged that it is, but that's nothing new.
"Every time I'm up there, I feel confident," said Rizzo, whose walk-off shot was the first for the Cubs since his game-winner on July 29, 2012.
"Whether I'm 0-for-5, 0-for-6, 0-for-10, 5-for-5 in these situations, I always say I want to be up there -- and my teammates, I want them to want me up there as well."
Slowey expected Rizzo to be hacking.
"I had a pretty good idea that Rizzo was going to be aggressive," Slowey said. "I wasn't able to get the ball where I needed to get it. He put a good swing on it."
Rizzo's homer extended Chicago's winning streak -- all at home -- to a season-high four games. It's the club's longest streak since a four-gamer last July 6-9, while the victory also improved the Cubs to 7-1 in their last eight games at Wrigley.
Rizzo's heroics allowed the Cubs to overcome Hector Rondon's ninth inning, in which Miami scored three runs to send the game into extras. The Cubs' closer allowed consecutive singles to Casey McGehee and Garrett Jones before Adeiny Hechavarria added another with one out to load the bases.
The Cubs recorded the second out after manager Rick Renteria successfully overturned a call at first base via challenge, but the victory was short-lived as Miami's Reed Johnson delivered a game-tying, pinch-hit two-run single.
"Rondon went in there to close it out and it didn't happen," said Renteria said. "But he kind of got chinked a little bit. Everybody else also came in and picked him up."
Cubs righty Carlos Villanueva pitched two perfect innings to earn the win, while Brian Schlitter added two scoreless innings of relief.
The ninth-inning collapse kept right-hander Jason Hammel from earning the victory, despite another gem in which he scattered six hits and fanned eight over seven shutout innings in his second consecutive scoreless outing.
"Obviously, very confident in my stuff right now, trusting it and having a good game plan," Hammel said. "These right-handed-heavy lineups that I'm getting a lot lately, I have the advantage."
As quiet as Hammel kept Miami's bats, he was arguably the game's second-best pitcher for much of the afternoon.
Marlins right-hander Nathan Eovaldi retired the first 14 batters he faced before Nate Schierholtz singled with two outs in the fifth inning for the Cubs' first hit of the day and Schierholtz's 500th of his career.
Two pitches later, Eovaldi's shutout bid was also gone, as Chris Coghlan laced an RBI double into right field.
Eovaldi allowed only one more hit until the eighth, when he wore down. Pinch-hitter Justin Ruggiano and Emilio Bonifacio knocked one-out hits before Rizzo pushed the Chicago lead to 3-0 with a two-run double to left that was misplayed by Miami's Christian Yelich.
Eovaldi was removed after 7 2/3 innings, allowing three runs on six hits and striking out eight while walking one.
"We got away with one today," Hammel said. "He was on his game and we got some timely runs there late."
Hammel wasn't quite as dominant -- allowing at least one hit in each of the first four innings -- but he pitched out of his only jam in the fourth by getting Eovaldi looking at a 93-mph heater after a seven-pitch at-bat.
Hammel retired the final six batters he faced before turning the game over the bullpen, which, aside from Rondon, threw five shutout innings.
"I think they're playing with a lot of confidence right now," Renteria said. "I think they're continuing to pick each other up. I think they're starting to feel and know that they can do this."