Like the one in Cincinnati on Sept.4, when Martinez inherited a tie game in the 15th inning and helped pitch the Cardinals to a crucial NL Central win with two scoreless innings. There was a show of poise and athleticism, the latter most evident on a stellar defensive play.
It was, Martinez says now, the game that made him feel he belonged.
"When they gave me the ball, they said they trusted me to go ahead and pitch," Martinez said through an interpreter. "It was after that game that I said I felt good, and I was able to build on that. They trusted me, and I delivered."
Manager Mike Matheny points to the night in Milwaukee, two weeks later, when he called upon Martinez after the Cardinals had taken a one-run lead in the top of the 10th. Hours before his 22nd birthday, Martinez fell behind the leadoff batter, 2-0. A visit from catcher Yadier Molina followed, and 10 pitches later, Martinez was pocketing the ball from his first career save.
His signature moment may vary by perspective, but not the effect. For Martinez, 2013 was the season in which he truly came of age.
"We had a lot of confidence in him right from the beginning," Matheny said. "The stuff was there. It was just a matter of how he executed. That took a little time. Throwing him into big situations -- sometimes by force and sometimes by choice -- helps you see what the guy is actually made of when he gets out there."
The foundation built by Martinez last season -- which also included 12 postseason appearances -- is one he hopes to fortify with his first full season with the Cardinals. And if he has his way, he'll do it in the rotation.
Martinez's pursuit of an Opening Day rotation spot turned tangible on Friday, when he became the first Cardinals pitcher to take the mound in a Grapefruit League game. A misplaced slider to Garrett Jones resulted in a two-run homer, but Martinez recovered to retire the next seven batters he faced.
His outs were quick. He avoided nibbling around the strike zone. And he showed promise with his curveball and changeup, both pitches Martinez said he would like to utilize more often this season. Adding those offspeed offerings to the four-seam fastball, sinker and slider, which he now throws from the same release point of his fastball, gives Martinez an enviable repertoire.
"You're looking at a kid, with four pitches and a pretty good changeup that is a work in progress," Matheny said. "He's still learning that he can use that in different counts to different hitters and it won't hurt him as much. I think he has made great strides so far."
There is much to absorb as Martinez reflects back on the past 12 months. At this time a year ago, he was missing out on an opportunity to participate in his first big league camp; visa issues grounded him in the Dominican Republic until late March. That briefly delayed the start of his season, but not Martinez's ascension.
Five weeks into the season, he was summoned as part of the Cardinals' desperate efforts to fix a porous 'pen. It would be one of three different stints Martinez had with the Cardinals, who then included him on each of their three postseason rosters.
He made only one start with St. Louis, but Martinez said the relief work heightened his awareness to "keep focused on the game." Of his 21 appearances, 15 were scoreless. Molina, who Martinez appears to trust implicitly, had much to do with positioning Martinez for that sort of immediate success.
"Yadi has been extremely helpful," Martinez said. "It was very important to have him and Mike always talking to me and telling me that they trusted me. He put a lot of emphasis on not thinking too much about the last play."
Martinez built off the 120 2/3 innings he pitched in 2013 with another 23 2/3 in the Dominican Winter League during the offseason. He capped that six-start stint with seven scoreless innings on Jan. 15. The work not only allowed Martinez the chance to get back into the routine of starting, but it positioned him to be ahead of most pitchers upon reporting to Spring Training.
That's made an impression.
"It's pretty universal that every time he walks off the mound and they walk out of the cage, it's a, 'Wow. That stuff looked good from the field, but I didn't really realize up close what it looked like,'" Matheny said, describing the reaction of his own hitters, who faced Martinez in live batting practice. "I think they all appreciate not just the stuff, but how he grew last year as a player with the experience that he got. It was a great learning experience for him."
Martinez's season-opening assignment will not entirely hinge on his spring. He has six starters with more Major League experience -- Adam Wainwright, Lance Lynn, Joe Kelly, Shelby Miller, Michael Wacha and Tyler Lyons -- to battle in pursuit of five spots. The Cardinals have also seen how valuable Martinez can be in the 'pen.
Whether his starting opportunity is brief (a la Trevor Rosenthal in 2013) or extends deep into March, Martinez merely wants further assurance that he belongs.
"As long as they give me an opportunity to be part of the club, I would be happy," Martinez said. "Also, I know that being on the team in the bullpen, if something were to happen with one of their pitchers, I can go and fill that role."