When Yordan Alvarez was with Class A Quad Cities in 2017, hitting coach Ben Rosenthal saw someone with plenty of power to all fields and an unwavering plate discipline. Now that the pair have reunited two years later with Triple-A Round Rock, Rosenthal has learned quickly that not much has changed for the slugger.

If anything, Alvarez has gotten better.

On Saturday, the third-ranked Astros prospect cranked a career-high three homers to power the Express to a 7-5 victory over New Orleans in the opener of a doubleheader at the Shrine on Airline. It was the first three-dinger game for Round Rock since May 8, 2011 when Taylor Teagarden had a hat trick.

Complementing Alvarez's performance, Derek Fisher went deep twice and drove in four runs.

"The power is there, everybody sees it, but I think what's really cool and fun to watch is when he locks it in," Rosenthal said of Alvarez. "His plate discipline and ability to hone in on a certain pitch and ability to lay off other pitches. That's what's really impressive -- when he tightens it in on the zone and he's only going after whatever he's committed to and he won't flinch at anything.

"I remember a couple of years ago when he was in [Quad Cities] when he didn't swing it was a ball; you couldn't call it a strike. He's really good."

With his 55-grade power tool, Alvarez broke through with a strong 2018, belting 12 homers for Double-A Corpus Christi before adding eight with Triple-A Fresno in 45 Pacific Coast League games. Overall, MLB.com's No. 43 prospect finished with a .293/.369/.534 line and 41 extra-base hits in 88 contests.

Gameday box score

A night after nearly being no-hit by No. 18 Marlins prospectZac Gallen and the Baby Cakes bullpen, Rosenthal said it was more than beneficial to have both Alvarez and Fisher find their strokes.

"It was great because we were almost no-hit last night, so it was definitely nice that they were able to go, 'All right, it's game time' and turn it on," Rosenthal said. "Fish had some great ABs, too. He even said last night that he was seeing it well and recognizing it well and just needed to get some swings off. Sure enough, they did their work today in the cage and went out and put it into play."

Alvarez went 0-for-3 on Friday in his first game in a Round Rock uniform but fared better in his second night with the club. In the second inning against starter Héctor Noesi , the 21-year-old broke the ice when he sent a solo shot over the left-center field wall.

In the fourth against the veteran right-hander, Alvarez worked the count full before smacking the sixth pitch over the left-center field fence again. Following Fisher's two-run blast in the sixth, the Cuba native fell behind reliever Mike Kickham , 1-2, but deposited the next pitch over the wall in center for his third solo shot of the game.

After Alvarez went deep for the second time, Rosenthal said there was some "chirping" in the dugout about the possibility of a third dinger.

"As a coach, at that point, I'm just being a spectator and watching to see what he's going to do," Rosenthal said. "I'm trying to give him info on the pitcher if we have it. He kind of goes up and has a plan. He takes whatever info we have and whatever else he sees. And I'm like, I'm just a fan, I'm having fun watching this, too."

It was the third career multi-homer game for Alvarez, who posted two-homer contests each of the last two seasons in the Astros system. He's hit 26 home runs since his time in the Midwest League, but Rosenthal said the outfielder has done more in the last two years than just crush long balls. The maturation process has helped Alvarez develop into more of a complete hitter, one who's on the cusp of reaching the Major Leagues.

"Just watching him grow, he's always been willing to listen and learn and do things," Rosenthal said. "It's always been in there. Like any player, he's refining his skills and learning himself a little bit better, what he can and can't do at the right time. ... It's like he's putting all of the pieces of the puzzle together and connecting all these dots. It's cool to see him do that and take off."

Fisher, who went yard in the sixth and seventh, had not hit two homers in a game in the Minors since May 12, 2016 with Corpus Christi. The 25-year-old followed up his two-homer opener with another solo blast in the nightcap, although it was the only run the Express scored in a 2-1 defeat.

Fifth-ranked Astros prospect Corbin Martin took the loss after surrendering a two-run homer to Matt Snyder in the second. Over 4 1/3 innings, the right-hander yielded two hits and three walks while whiffing three in his Triple-A debut.

For New Orleans, No. 4 Marlins prospect Nick Neidert earned the win after limiting Round Rock to one run on four hits and three walks with four punchouts in 5 2/3 innings.