Though far from complete at all positions, the Astros' Minor League system is miles from where it was over a year ago, when general manager Jeff Luhnow took over.

Two Drafts later, and with a slew of trade acquisitions developing well, the system is now among the best in baseball, according to almost every third-party ranking.

"It's been an overhaul of not only some players, but the philosophy on how we're building the Minor Leagues," Luhnow said before last week's First-Year Player Draft. "To see the kind of talent we have now -- our affiliates have the highest combined winning percentage in baseball -- it's a sign of things to come."

It all starts with first baseman Jonathan Singleton, the club's No. 1 prospect as ranked by MLB.com. After returning from his 50-game suspension, handed down for violating Major League Baseball's drug policy, Singleton has ascended to the Double-A squad in Corpus Christi.

Astros manager Bo Porter, who took Singleton under his wing during Spring Training, said the slugger could have already been playing in the big leagues if not for the suspension.

"If you put that situation aside, he absolutely would have competed for the 25-man roster," Porter said. "It's only made him hungrier and more eager to perform at a high level. When you take a person of his skills and you add that motivation, it's very beneficial."

Luhnow hasn't ruled out Singleton showing up in Houston by summer's end.

"Why not?" Luhnow said when asked if Singleton could play for the Astros this season. "Maybe this will all end up with him in Houston soon."

After Singleton, the Astros' Minor League strengths lie up the middle and in right-handed pitching.

Last year's No. 1 overall pick and the Astros' current No. 2 prospect, shortstop Carlos Correa, is still young, but he's flashing some pop with his bat to go along with a flashy glove for Class A Quad Cities.

Two other shortstops rank among the club's 20 best prospects, with Nolan Fontana and Jonathan Villar starring at the high Class A and Triple-A affiliates, respectively.

Delino DeShields, the organization's No. 5 prospect, is Fontana's double-play partner for the Jethawks, and they could eventually bring their double-play prowess to Houston.

With their first two picks in this year's Draft, the Astros added two right-handers, Stanford's Mark Appel and UC-Irvine's Andrew Thurman. If the two sign, they'll join an impressive array of young arms in the system that includes Jarred Cosart, Mike Flotynewicz, Asher Wojciechowski, Lance McCullers and Vincent Velasquez, all of whom are among the organization's top prospects.

However, none of those pitchers is widely projected to be a front-line starter in the big leagues, and none of them is left-handed.

Along with catcher, left-handed pitching is the farm system's primary weakness. The Astros added North Carolina southpaw Kent Emanuel in the third round of the Draft.

"Those Draft additions come at the right time in our system, because they give us real dominant potential and some variety with a lefty," said Mike Elias, director of amateur scouting. "We've already got young arms starting to perform, but you need the experience to challenge the youth."

Overall, the Astros potentially injected four catchers and 24 pitchers into the farm system with this year's Draft class.

Two of the Astros' top 20 prospects have seen time in Houston this year, with reliever Brad Peacock and outfielder Robbie Grossman appearing in a combined 37 games.

More reinforcements are sure to follow, though perhaps the wave is more likely to arrive in 2014 or 2015.

Six of Houston's top prospects are on the Double-A Corpus Christi roster, including some of the organization's most powerful bats. Singleton and outfielders George Springer (Houston's No. 3 prospect) and Domingo Santana (No. 13) form a formidable middle of the order, one with Major League pop.

"I'm pretty excited about the lineup right now in Corpus," Luhnow said last week, when center fielder Justin Maxwell was on assignment there. "You've got a lot of thunder in that lineup. The future is exciting, and having Justin there to help them along for a while is a plus."

Elias expects to see that group form the core of the Astros in 2015 and beyond.

"We hope and expect to see that," he said. "You will start to see waves of players poking their heads into the big leagues this fall and continuing to do so throughout the next few years.

"More than anything, after the shape the system was in before, we're hoping that movement is consistent. Building the Minor League system isn't a one-time process. We want a continual pipeline arriving, and doing that sustains a contender. We're almost there, and so is that young talent."