If you’re a baseball player growing up in New England, you’ve probably fantasized at some point about stepping to the plate at Fenway Park with the game on the line and a chance to win it with one swing of the bat.

For Mickey Gasper, that dream became a reality in the bottom of the 10th inning Monday night.

Barely six hours after he’d received the call he was coming to Boston, the Red Sox rookie was thrown right into the fire late in Monday’s extra-innings win over the Texas Rangers. The switch-hitting catcher pinch hit for David Hamilton with two men on and one out, and he worked a tough seven-pitch walk against Rangers lefty Walter Pennington to load the bases.

Two batters later, Rob Refsnyder sent the Fenway Faithful home happy with a walk-off single to give Boston a badly needed 5-4 victory.

“That at bat by Mickey, phew,” manager Alex Cora said afterwards. “In that moment to be able to walk, that was impressive, that’s the reason he’s here.”

“It’s just a blessing,” Gasper said. “I’m really thankful that AC had the confidence in me go up there and put together a good at bat and the team giving me that chance and putting me in that spot to let me showcase what I can do up there.”

Originally acquired in the minor league phase of the Rule 5 Draft this past offseason, Gasper wasn’t envisioned as a big league contributor but has turned heads throughout the organization ever since his arrival. After performing well and earning a promotion from Double-A early on, he’s batted .402 with a .515 on-base percentage in 40 games at Triple-A Worcester.

That performance earned him a reputation in Boston before he ever stepped foot in the Red Sox clubhouse, a reputation he lived up to on Monday.

“He seemed very calm, I’ve heard great things about his at bats,” Refsnyder said. “I think it was 2-2 or 1-2 he took a really good slider low. Most guys in that moment, I know I would have swung over the top of that one. A lot of credit to the player development, the Triple-A staff getting him ready, but a lot of the credit goes to him. That was a huge at bat and he did his job.”

Gasper, who grew up in Merrimack, N.H., and played college baseball locally at Bryant University, has attended numerous games at Fenway Park as a fan. While his family weren’t able to make it in time to see his debut — they now live in New Jersey and wouldn’t have had enough time to make the drive before first pitch — several friends and former teammates were able to hustle in to see him play.

And as nerve-wracking as you’d think the situation would be, Gasper said he felt calm and relaxed when he stepped into the box for the first time.

“I was so calm up there, I don’t know what was going through my head, I felt good, I guess I felt like I was at home,” Gasper said. “I was relaxed, saw the first couple of pitches, I was a little upset he dotted that sinker on me, that was a good pitch to hit, but that’s alright, I moved on and kept my breathing, stayed composed and had some fun with it.”

One thing that also helped was that Gasper had a false start earlier in the game that got the initial jitters out. When Rangers closer Kirby Yates first entered the game in the eighth a lefty was also up warming, so Cora told Gasper to get ready. When Yates took the mound instead he got to sit down, take a deep breath, and prepare himself for when the lefty eventually came the next time through the order.

“I had a feeling I was going in so I was mentally prepared for that lefty,” he said.

After the game the Red Sox celebrated Gasper’s big league debut with a beer shower, and the 28-year-old was also gifted the game’s lineup card and some other trinkets to commemorate the occasion. Gasper said the most important treasures will live in his memory, but that the beer shower was something he probably couldn’t have imagined would be happening when he woke up earlier that day expecting a quiet day off.

“I’ve never done anything like that,” Gasper said. “It was fun.”