At times during his outing, Miley appeared as if he would make the choice abundantly clear, striking out a career-high 10 batters and sitting down 12 straight during the middle frames.
But with four outs remaining in the game, the southpaw couldn't finish the job, leaving the mound for the final time in 2012 with his head hung in disappointment, unable to secure a victory.
"I didn't make some pitches at the end," Miley said. "I have to forget about those things now and take a positive into the offseason."
Before the eighth, the only blemish on Miley's otherwise spotless night came courtesy a solo home run off the bat of fellow Rookie of the Year candidate Wilin Rosario.
But after a bunt single by Charlie Blackmon began the eighth, Josh Rutledge and Tyler Colvin both doubled to bring home the game-tying and go-ahead runs to spoil Miley's evening.
"I left a fastball and a slider out over and they made me pay," Miley said. "I just wanted to compete. I wasn't able to finish it off in the end."
On any other night, D-backs manager Kirk Gibson probably would have gone to the bullpen earlier. But on Monday, he wanted to give his pitcher a chance in his last appearance of the season.
"I let him go longer than I probably would've normally, but it was his last start," Gibson said. "Usually in those situations, you don't let a guy lose a game like that, but Wade wanted to pitch so I let him go, it ended up biting us. He threw the ball well though."
Luckily for Miley, Paul Goldschmidt was there to save him, taking the rookie off the hook for the loss with a game-tying homer in the ninth to send the game to extras at 3-3.
"Obviously it's nice to at least get him a no-decision," Goldschmidt said. "You'd like to score more and get him the win though."
Earlier in the night, the rookie struck out the Rockies' side in the third on just nine pitches, becoming the second Major League pitcher this year and third in franchise history to accomplish the feat.
Including Monday's start, serving up three earned runs on six hits over 7 2/3 innings, Miley will end his season with a 16-11 record and a 3.33 ERA. In six of his losses, however, the lefty allowed three earned runs or less.
"It's been rough, we've had some games thinking about where he's pitched really well and took a loss," Goldschmidt said. "I'm a little biased, but he's been huge for us. Just what he's been able to do, he's thrown a ton of innings. I don't know the rest of the guys' numbers, but he definitely deserves to be in contention."
Miley's main competitors in the rookie voting include Nationals outfielder Bryce Harper and Reds first baseman Todd Frazier, both of whom are on playoff teams.
Regardless of his eventual finish in the balloting, Miley's year was undoubtedly one of the more improbable of 2012. The 25-year-old barely made the 25-man roster out of Spring Training, starting the year in the bullpen before moving into the rotation in the middle of April.
Miley was the sole D-backs player to be selected for the All-Star Game, winning nine games before the break.
The southpaw continued his memorable season in July and August, but ran into trouble in September, finishing the month 2-2 with a 5.40 ERA, including Monday's struggles in the eighth inning.
"It's bittersweet, I always want to get better," Miley said. "I'll work harder in the offseason and try to get better, more consistent throwing strikes. I hadn't had too much success over the last month so I just wanted to come after guys.
"I'm not an individual type though. I experienced going to the playoffs last year, so that was my main goal. I didn't set many personal goals at all, just help the team win."
Before Goldschmidt's ninth inning homer, the only offensive support the D-backs provided Miley on Monday came on solo homers from Aaron Hill and Gerardo Parra.
While the rookie's potential recognition seems to be up in the air, Hill figures to deliver at least one piece of hardware for the D-backs. Leading all NL second basemen in on-base percentage, home runs and RBIs, the 30-year-old is a front-runner for the Silver Slugger Award.
Brad Bergesen took the loss for the D-backs on Monday, as he was charged with all four runs in the 13th. As a whole, the Arizona bullpen walked four batters and threw two wild pitches in the final two frames.
"We battled, but we got pretty sloppy there," Gibson said. "The bullpen walked four guys, that's killer and indicative of what we have done. Those things, even though the season is coming to a close, are frustrating."