VIERA, Fla. -- The starter-stacked lineup Cardinals rookie Shelby Miller hoped to face against the Washington Nationals in his first start of spring training was the kind that would have unnerved him in previous springs.

"A year ago, I was pretty much intimidated by a team like that," Miller said after his three innings against the Nats' regulars Friday. "I was younger. I had no big-league experience. My main goal (Friday) was to go out there and control the game, work on every pitch I had."

He did most of that in one prolonged at-bat by Washington's Bryce Harper.

In his second appearance of spring, Miller continued auditioning for the fifth spot in the Cardinals' rotation with three strong innings on a good day to hit at Space Coast Stadium. Miller allowed two runs on three hits and a walk while the Cardinals drubbed the Nats, 16-10, in an exhibition game. Harper, the reigning National League Rookie of the Year, produced both runs off Miller with a two-run triple in the third inning. But it was Harper's 11-pitch at-bat in the first inning around which Miller's start hinged.

Some time during Harper fouling off four consecutive pitches and before Miller fired a 95-mph fastball past Harper for the strikeout, the at-bat became spring training in name only.

Miller called the showdown "fun."

"I thought it was fun, too," manager Mike Matheny said. "You see two guys who are highly touted and it's a great opportunity to bring the best out of somebody. It wouldn't be out of the question to see a young pitcher not perform in a situation like that. He did that. ... He's matured. He does have a better composure than what he had last year."

The Cardinals' highest-rated pitching prospect, the 22-year-old Miller is dueling roommate, close friend and future groomsmen Joe Kelly for the opening in the Cardinals' five-man rotation. A three-way heat entering spring training, the attention has locked on Miller and Kelly in the recent days with righty Trevor Rosenthal moving to the bullpen. In their previous starts, Rosenthal and Kelly were both overanxious and, at times, unsteady with their command. Rosenthal walked two batters in his first start, acknowledging he was trying to impress. Kelly has five walks in his first two starts and talked about searching for rhythm in Friday's start.

The Nationals greeted Miller with a lineup that featured six of the team's everyday starters, including Harper batting third and All-Star Ryan Zimmerman at cleanup. Second baseman Danny Espinosa drilled a lead-off double to the center-field wall, but Miller retired the next three batters, including the strike out of Harper, to end the inning.

It took him eight pitches to get three outs in the second inning.

And only Harper's hot-shot groundball that bounded over first baseman Allen Craig's leap and into the right-field corner kept Miller from a scoreless outing. He threw 56 pitches, including 34 strikes.

"The deeper and deeper we go into spring the more you're going to be concentrated on -- on how you do on all things," Miller said. "Whether that's how you're doing, how you're pitching, how you're getting hitters out all the way to your mound presence and how you're handling situations. I know it's getting down to the wire where they need to make a decision."

The schedule allows for at least one more turn through the rotation with both Kelly and Miller getting the necessary innings to build strength, pitch count and stamina. They could piggyback in a game next week, but the opportunities to start both games is dwindling with opening day less than 31/2 weeks away. Matheny said the team needs to identify a fifth starter so that he can build his pitch count closer to 100 before leaving Florida.

While pitching for his future, Miller often mentioned his past Friday.

He described how a younger him would have been less-equipped to face a lineup with that many major-league regulars. He illustrated how he threw off-speed pitches when behind in the count Friday, something he rarely did as a fastball-chucking minor-leaguer. He said a year ago those fastballs would have hit 88 mph because he lacked strength in spring. Nats outfielder Tyler Moore said Miller's fastball had "giddy-up and gets on you quick" Friday. Miller allowed that he had more pitches and more faith in those pitches to outlast Harper. But he also had the fastball when he needed it.

He tested Harper with several 94-mph fastballs before elevating at 95 mph.

"I wanted to rear back and get something on that," Miller said.

"He has the ability to pitch up in the zone," Matheny said. "The ball gets on hitters a little different with him than guys throwing harder than him. I think there are some things that he brings to the table."

And there are the things that Miller literally brings to the table.

Miller credited the waffle with syrup that he has every morning for some of his success. Slimmed down to 204 pounds last spring, Miller lost strength and, he said Friday, "had to learn from that mistake." This spring he reported at 223 pounds and, thanks in part to the waffles, he's around 230 pounds. He believes that has given him strength this spring that he didn't have last season. That puts some muscle behind the poise and confidence his coaches have complimented.

Maintaining all of those traits is the next step.

"I eat everything in sight," Miller said. "I'm going to go eat a blueberry muffin."

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