But think back to Tulowitzki's play on pinch-hitter Wladimir Balentien's seemingly certain single up the middle, which became the second out of the seventh, with the score tied at 3. Drew Sutton walked and Adam Rosales singled against Aaron Cook. The hit could easily have put the Reds ahead.
Instead, Franklin Morales (2-0) replaced Cook for the most important out of the game, a fly ball by Joey Votto. In the next half-inning, Iannetta and Gonzalez went deep against David Weathers (2-3).
Tulowitzki's play helped make the surge possible for the Rockies, who improved to 2-3 on the current road trip. They entered the night a game behind the Giants in the National League Wild Card standings.
"When you look back on those plays, they help," said Tulowitzki, who doubled in a first-inning run. "It seems every time we make one of those plays, they've gotten a hit after it. Nobody realizes that. But I know our pitchers appreciate it."
Cook and an increasingly sure bullpen -- which the Rockies hope they've enhanced by acquiring left-hander Joe Beimel from the Nationals before Friday's non-waiver Trade Deadline -- can thank the defense for the victory.
The offense struggled early, not making the most of six walks and four hits against the Reds' Justin Lehr, who was making his first Major League start. The Rockies managed three runs in five innings against Lehr, but other than Tulowitzki's double the other runs scored on outs -- Brad Hawpe's fielder's choice in the first inning and Iannetta's sacrifice fly in the third.
"We need to score some more runs in certain situations, but we're battling and doing all the little things right," Rockies second baseman Clint Barmes said.
It came down to defense and pitching. Cook worked 6 2/3 strong innings but lost his chance at a victory when Votto and Brandon Phillips hit consecutive solo shots to tie the game, 3-3, in the sixth. And he had plenty of help.
Barmes set the tone by siding into the grass in short right to rob Votto of a hit at the end of the first inning. Center fielder Gonzalez made a diving grab of Laynce Nix's tricky fly ball in the fourth -- with a runner on first who might have scored had Gonzalez missed. Before Tulowitzki's masterpiece in the seventh, Cook knocked down Ryan Hanigan's hard bouncer, chased the ball behind the mound and made a prompt throw.
"You can beat us, but if you do, you have to do a lot of things right and earn everything you get, because we don't surrender a whole lot," Rockies manager Jim Tracy said.
On a perfect evening, Cook would have won. He and Tracy are products of Hamilton, Ohio. Both received keys to the city in pregame ceremonies. Cook could have broken the game open in the third had Rosales not made a diving catch of his bases-loaded line drive to end the third.
But Cook is more concerned with the team winning than storybook endings.
"At no point during the game did I feel like I lost control," said Cook, who gave up seven hits, struck out four and forced 10 groundouts. "The main thing is we got a win. We're in a Wild Card race right now. It doesn't matter who gets the win."
The big hits came from players who needed them. Iannetta's homer, his 12th of the season, displayed a natural power that makes his low .226 average look out of place. Gonzalez, who has two homers, is a young talent who will be in and out of the lineup as the Rockies go for victory over development.
The Rockies' solid pitching and defense makes it easier for anyone to fight through slumps and growing pains.
"We just need to keep pitching and guys to keep stepping up," Iannetta said.
Tulowitkzi didn't just step up. He leaped, twisted and bounced a throw to stretching first baseman Todd Helton to give his team a chance to win the game. And he enjoyed discussing it.
"You're asking a person who takes pride in defense, and wants to play good defense," Tulwitzki said, smiling. "That's the reason we're winning games. Too many teams don't realize that."