He earned the assignment not only for how he performed in the spring, but for the progress he showed during a 2012 season that included several parts adversity, reflection and resurgence.
"I just think he's radically changed," manager Mike Matheny said. "He knew that there were some things he was doing early on keeping him from getting here and he changed and he was rewarded and then he said, 'This is who I need to be.' It was a transformation."
One facet of that growth process last year keyed his ability to capture his first win as a starter.
As he did throughout Spring Training, Miller opened the afternoon unafraid to attack with his breaking pitches. He left a few of them up, though, which set up Hunter Pence's second-inning solo homer and the Giants' two-out run in the third. But rather than abandoing the pitch -- something Miller had a tendency of doing when things didn't go right in Triple-A -- and, in turn, relying too heavily on his fastball, Miller continued to follow catcher Yadier Molina's lead and throw his curveball.
The location of the pitch improved and so, too, did the results. Miller did not allow another run in his 5 1/3-inning outing.
"That is just the lessons I have to work on in my bullpens," Miller said. "Making sure I get the balls down in those situations and trusting my curveball in those kinds of situations as well, being able to throw it when it's necessary."
Miller did walk four of the final nine batters he faced -- a product of a sometimes errant fastball. But none of the four advanced to third.
That was in part due to an assist from first baseman Allen Craig, who snagged a sharp line drive to start an inning-ending double play in the sixth. The pair of outs came on the first pitch from Randy Choate, who relieved Miller after two consecutive walks.
"He's going to come in big situations and have to get big outs," Matheny said of the lefty specialist, who, because of the Giants' decision to pinch-hit for Gregor Blanco, instead faced a righty in the sixth-inning spot. "Regardless of how it happens, just get them out."
Though Miller didn't pitch deep enough to qualify for a quality start, he did earn his second Major League win. His first came in relief last September. Miller struck out four in Saturday's 95-pitch effort.
"He pitched well," Giants manager Bruce Bochy said, "and did a good job of holding us down."
Entering the day having scored one run in their previous 18 innings, the Cardinals matched that just five hitters into the game. In the end, the club manufactured six runs on 11 singles. Three of those were infield hits, all of which led directly to a run. A pair of sacrifice bunts and a stolen base also set up scoring opportunities.
The club went 6-for-10 with runners in scoring position and scored four of its runs with two out.
"When we're not really banging the ball all over the place, we're going to have to do the little things right," Matheny said. "Two-out hits, too, those are big. I thought it was pretty well-rounded today."
Beltran, who entered the day with one hit and no RBIs in the first four games of the season, was routinely in the middle of the Cardinals' activity. His two-out bloop single to right scored Matt Carpenter in the first.
Four innings later, he followed Matt Holliday's two-out RBI single with a two-run single to right.
"It's a good team. We have a good lineup," Beltran said. "We have guys from top to bottom that can do the job. When [David] Freese comes back [from injury], we're going to have another guy who can be a threat in the lineup. It's fun because as a player you just want to go out there and be part of it."
Pete Kozma finished with a multi-hit game as well, pushing his early-season average to .350 with hits in his first three at-bats. His infield single started the fifth-inning rally. In the sixth, he cushioned the Cardinals' lead by driving home Daniel Descalso.
The Cardinals gladly took the insurance run, as they allowed the Giants to creep close late. Edward Mujica, pushed into eighth-inning duty due to Rosenthal's unavailability, was tagged by Sandoval's leadoff homer on his second pitch of the inning. Buster Posey followed with a double, though San Francisco didn't score again in the frame.
After Carpenter added an RBI single in the ninth, Mitchell Boggs entered with the opportunity to rebound after blowing his first save chance of the year Wednesday. Boggs, the team's fill-in closer while Jason Motte is out, earned his first save since 2011 with a 10-pitch inning.
"For me personally, it was good to go out there and have a good inning," Boggs said. "I don't harp on my good outings, so there's no reason for me to do that with my bad ones. You try to learn as much as you can from all of them and be better in the next one."