Reynolds' first playoff game mirrored his rookie season in the big leagues, which was full of peaks and valleys.
The third baseman threw a grounder into the seats, allowing Chicago's leadoff man in the fifth to reach second, and looked bad striking out swinging on a high fastball in the fourth, something he did 129 times in the regular season.
However, after laying off a pair of nasty sliders, Reynolds pounded a Carlos Marmol fastball out of the ballpark in the seventh inning.
"Mark will punch out a couple times and then you make one mistake and it ends up in the seats," manager Bob Melvin said. "We've seen that all year. It was nice to see him recover from throwing a ball away. He's played flawlessly defensively basically all year, and I know it bothered him a little bit."
After jumping out to a hot start with a .426 batting average to go with four homers and 15 RBIs in the first two weeks after his call up on May 16, Reynolds cooled a bit, hitting .162 in June and .194 in July. Although he heated up in August, the rookie also tied a Major League record with nine straight strikeouts at one point.
After that, he turned the corner for good, hitting .342 in August as a whole and .300 in September, while providing Arizona with a consistent power source (nine homers, 31 RBIs) in the final two months.
"I definitely started out hot and then the book was kind of out on me after that, and definitely I went on a little roller-coaster ride there for a while," Reynolds said. "In August and September, I was able to make some adjustments and turn it around a little bit, and I'm just glad I made it at the right time, going into the postseason."
All season long, Melvin has stuck with the third baseman through his ups and down, pointing to the fact that even when Reynolds struggles, he can always run into a pitch and change the game, precisely what happened in his playoff debut.
"We've seen enough of Mark to know that he's going to go out there and play his game," Melvin said. "He's going to be aggressive defensively, aggressive offensively."
Although many national pundits have pointed to Arizona's inexperience as a detriment, in the end it came down to a rookie putting the D-backs over the top in Game 1 against the Cubs.
That came as no surprise to starting pitcher Brandon Webb, who earned the win off Reynolds' support.
"They're part of our whole team," Webb said. "They've been doing it all year and doing a great job at it, defensively, offensively and everything. Even though they're young and rookies, a lot of them, they don't play like rookies, so we've got total confidence in them, throwing them out there every day."
That loose attitude can be an advantage, such as when Reynolds stepped to the plate in a tie game in the playoffs against Marmol, who entered the game with 1.43 ERA in the regular season.
None of that mattered three pitches later, when Reynolds sent a ball flying to the right-center-field seats.
"All of us young guys were kind of thrown in the middle of this, and we kind of don't know what's going on," Reynolds said. "Personally, I don't realize the magnitude of the situation that we're in, but just go out there and having fun and playing ball, and that's what we know how to do, and we've been doing it all year."