Monday night's game in Houston between the first-place Kansas City Royals and the first-place Houston Astros was a fascinating matchup beyond the first meeting of the season between two potential playoff teams. It presented a stark contrast in team-building philosophies and the state of each team's rotation. It presented an old guy versus a young gun, a 34-year-old veteran trying to hang on versus a 21-year-old just getting his cleats dirty in the majors. It gave us Joe Blanton versus Lance McCullers Jr., both pretty amazing stories.

Blanton started for the Royals, his third start of the season after a handful of relief appearances. He wasn't supposed to be here. He didn't even pitch in the majors in 2014, retiring after two Triple-A starts for the Oakland A's, saying his "heart wasn't in it." In 2013, he went 2-14 with a 6.04 ERA for the Los Angeles Angels. He might have been the worst pitcher in the majors that year.

How did he get here?

The Royals invited him to spring training, even though their rotation was set with Yordano Ventura, Jeremy Guthrie, Jason Vargas, Edinson Volquez and Danny Duffy. Former Atlanta Braves starter Kris Medlen, rehabbing from Tommy John surgery, had signed a two-year contract. Later on in spring training, the Royals signed Chris Young, who had a solid 2014 for the Seattle Mariners. Brandon Finnegan, last year's first-round pick who pitched out of the bullpen in the postseason, would be stretched back out as a starter. That left Blanton ninth on depth chart, and that's probably being generous.

"I actually enjoy the getting-ready part of it. If I don't mind that, why not just give it one more try and see what happens?" Blanton said in late February. "It got to a point where I made it not fun for myself. Now, I'm trying to make it fun again. If the talent is gone and it's not meant to be, I'll be able to walk away with a clear mind for good."

McCullers wasn't supposed to be here, either. Oh, he was on the prospect radar, the 41st overall pick in 2012 with a blazing fastball, the son of former major league reliever Lance McCullers Sr. The Astros signed McCullers to an over-slot $2.5 million bonus with extra money saved by taking Carlos Correa with the first overall pick and signing him to a below-slot deal (I'd say both selections worked out well). But McCullers had just 228 innings in the minors entering 2015, none of them above Class A, and recorded a 5.47 ERA at Lancaster in 2014, walking 5.2 batters per nine innings. With numbers like that, McCullers was just trying to make the Double-A team in camp. He did so, made six appearances and then was called up in mid-May after striking out 43 in 29 innings while cutting his walks.

No team makes it through the season with five starters, of course, and eventually the Royals were forced to turn to Blanton, who made six starts at Triple-A before getting called up for relief duty. After beating Felix Hernandez last week with six innings of one-run baseball, Blanton labored through 74 pitches against the Astros, getting knocked out in the third inning. McCullers had another terrific effort with seven innings, four hits, one run, two walks and six strikeouts and improved to 4-2 with a 2.19 ERA through nine starts as the Astros won 6-1.

The difference in raw ability was evident: Blanton threw 45 fastballs, just 13 of them 90-plus mph and the hardest a 3-2 pitch in the second inning to Domingo Santana that registered 91.5; McCullers threw 63 fastballs out of his 102 pitches, averaging 93.1 mph and topping out at 95.9 mph with a seventh-inning 0-2 heater to Alex Rios, the next-to-last batter he faced.

The key inning might have been the top of the first. Jarrod Dyson led off with a double, and after a fly out and strikeouts, Kendrys Morales walked. But McCullers got Salvador Perez to ground out on an 0-1 curveball. That's the pitch that's been the difference-maker for McCullers. Batters are hitting .105/.148/.132 against it; in 81 plate appearances ending with a curve, 39 batters walked back to the bench after striking out.

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McCullers throws his curveball to two locations: Against righties, it's down and away; against lefties, he uses it more as change of pace, and it comes in over the middle of the plate and middle-away. Either way, it's been effective.

McCullers' rapid development ranks as one of the more important stories of 2015. The Astros entered the season hoping to rely on Dallas Keuchel and Collin McHugh as a solid one-two punch in the rotation. The rest of the rotation was a concern. McHugh is 9-3 but has a 4.51 ERA. McCullers has become the team's No. 2 starter, and if McHugh comes around -- he's had better results his past two outings -- and when Scott Feldman returns after knee surgery, maybe the Astros don't have to add another starter.

In part, that's because general manager Jeff Luhnow and manager A.J. Hinch are trusting the young guys. Besides McCullers, Vincent Velasquez -- with just 26 1/3 innings above Class A -- is also in the rotation (he has a 3.72 ERA in four starts). Mark Appel, just promoted to Triple-A, might be next in line for an opportunity (although he gave up seven runs in his Triple-A debut).

Contrast that with Dayton Moore and Ned Yost with the Royals. Blanton, while a good comeback story, really smells of a desperation move; a playoff contender shouldn't be using him in its rotation. But the Royals don't trust their young guys: Finnegan is back in the bullpen and John Lamb has a 2.71 ERA at Triple-A with better numbers than Blanton had there. Meanwhile, Jeremy Guthrie, 36 years old, has a 5.68 ERA and has allowed the second-highest batting average among MLB starters (remember, that's with the league's best defense behind him). The rotation is 22nd in the majors in ERA, and that's with decent work so far from Young and Volquez, which might not continue.

Yost doesn't ask a lot of his rotation -- Royals starters have the fewest innings in the majors -- but as the Royals and Astros battle for AL supremacy, it will be interesting to see how the rotations play out. Right now, I'm liking the Astros' youngsters a lot more than the Royals' retreads.