Martinez hit an RBI double to straightaway center fielder in his first career at-bat -- a pinch-hit appearance in the eighth inning -- in the Astros' 6-2 loss to the Brewers on Saturday night. Martinez arrived at the ballpark about 90 minutes before the first pitch after being called up from Double-A Corpus Christi.
"It was definitely exciting," he said. "You go up there to the plate and my mind was just, 'Hit something hard. Don't embarrass yourself.' I got lucky that he left a fastball middle-away, and I was able to put a good swing on it. My eyes just lit up on it."
Martinez is expected to make his first career start in Sunday's series finale.
"There's a lot of excitement," said Martinez, whose parents flew in from Florida to see his debut. "It's a dream come true, and you work your whole life to get this opportunity. I'm thrilled and excited that they're giving me an opportunity."
Astros manager Brad Mills said that Martinez will play, though it's unclear if he'll play more in right field to replace Hunter Pence or left field when Carlos Lee sees time at first base. Martinez has more experience in left, but says he can play right.
"We're not bringing him up here not to play," Mills said. "We want to see this guy play. We saw how he could swing the bat in Spring Training and he played extremely well."
Martinez, 23, hit .338 with 13 homers and 72 RBIs this year at Corpus Christi after batting .341 with 40 doubles, 18 homers and 89 RBIs combined last year at Class A Lexington and Corpus Christi. He believes he's getting called up at the right time.
"The front office knows what it's doing and how to develop a player," he said. "If they kept me there and wanted me to learn, it's for a reason. I had the confidence in that. I'm not in a rush to get up here. I wanted to be up here, but I wanted to make sure I'm ready. That's the most important thing."