The 39th overall pick in this year's Draft debuted in mid-June in the Rookie-level Arizona League, where he proceeded to set the league record for home runs at 18 in 43 games.
Then Sunday, in his fourth game since a callup to Class A Short-Season Spokane, he belted his first two longballs and drove in seven runs in his home debut to lead the Indians in a 16-4 rout of the Tri-City Dust Devils.
"It was unbelievable. I can't even explain it, I was just so excited to have a game like that," said the 18-year-old. "It was an amazing atmosphere, first game I played there, so I didn't really know what to expect. But there was like 4,000 people there. I didn't really get to notice anything, just take in the moment and enjoy it."
Gallo was taken in the first round in June by the Rangers out of Bishop Gorman (Las Vegas) High School, and made his first professional appearance June 20 in the AZL after signing with Texas.
The 6-foot-5-inch, 205-pound third baseman went 0-for-5 in his first three games, but showcased his other commodity -- patience -- by walking nine times. He then hit his first home run in his fourth pro game, the first of his record-setting 18.
He finished with a .293 average in 150 at-bats with the AZL Rangers, adding 10 doubles, 37 walks and 52 strikeouts to post a .435 on-base percentage and a .733 slugging percentage, earning him the callup to the Indians.
In his brief introduction to the Northwest League, he's displayed that same power/patience combination.
"I've been happy with what I'm showing power-wise," he said. "I couldn't imagine how many home runs I would hit in the AZL and stuff. I definitely didn't come in thinking I would've done that.
"I didn't expect to come out and be a star, I wanted to just have fun and try and enjoy my first year. Let things fall into play, take it day by day."
After Sunday's outburst, Gallo is hitting. 313 for Spokane with a .389 OBP and a .750 slugging mark. Overall this season, he's hitting .295 with 20 home runs and 50 RBIs between the two levels.
The Nevada native said the first thing he noticed about professional ball was just how much work it actually was.
"Playing every day now, traveling, being at the field sometimes 10 hours a day, it's been a grind," he said. "I was very surprised at how much work it is. I knew it would be tough, but you don't really see that when you watch a baseball game, how much goes into it. It definitely has its rewards though."
Gallo added that, for now, he's just enjoying soaking in the Spokane atmosphere and learning as much as he can.
"There's not many people there to watch the games [in the Arizona League], just scrimmages to get your feet wet," he said. "It helped me a lot, being able to adjust to the pitching from high school and get a feel for pro baseball. But it's night and day [between the AZL and Spokane], going from playing in front of 10 people to 4,000 people.
"I'm ecstatic. I wanted to play in Spokane for a while, I knew how great of a team it is and what the atmosphere is like. I'm real excited."
Left fielder Royce Bolinger also went 3-for-5 with a triple, three RBIs and three runs scored while extending his hitting streak to 20 games. Christopher Garia added three hits, including a double, four runs and an RBI.
Connor Sadzeck (1-3) picked up the win, scattering two unearned runs on one hit and four walks while fanning four over six innings.