So much for that plan.
As Castellanos returned to the dugout in the seventh inning, having swung and missed at an Aaron Crow pitch in the dirt with a runner on third, his teammates tried to give him the same simple advice. The runner had scored on the pitch in the dirt, but as much as Castellanos had prepared himself, the game had gotten away from him.
Before the strikeout, there was the well-intentioned but ill-advised decision to try to take second on a line-drive hit to left, leaving Castellanos an easy target for Gold Glove Award-winning left fielder Alex Gordon's first assist of the year. It marked the thin line between baserunning aggressiveness and baserunning awareness. Castellanos also misjudged how much room he had on a foul ball near the third-base stands, resulting in a misplay but no error.
Simply put, Castellanos was trying to do too much.
"Just relax," Castellanos said after the game. "It's so easy to think but so hard to do. First big league Opening Day, at home, in front of all these fans -- it's easy to press. I had a lot of players after my third at-bat, when I swung and missed at a pitch in the dirt, which is not me at all, everybody said, 'Relax. Don't try to do too much. Be yourself.' I felt like I did a really good job of that in my last at-bats."
Manager Brad Ausmus put a good amount of faith in Castellanos that he would come up big, pinch-running for Alex Avila with Tyler Collins in his Major League debut in the ninth inning of a tie game. If Castellanos could relax and have a typical at-bat, slashing the gap in right-center, Collins would have a chance to go from first to third with one out, setting up the potential winning run to score without the need for a base hit off the Royals' vaunted bullpen.
Castellanos delivered. One batter later, so did Alex Gonzalez. When his hit got through the drawn-in infield, Castellanos was the first to mob him. Both celebrated their first Opening Day as Tigers with a rough start and a much better finish.
"Nick and I played together for 60 games in the Florida State League," Collins said. "He's special. He's a very handsy, very instinctive, very reaction-based hitter. He's got a lot of talent and he's blessed."
Talent has never been a question with Castellanos. His manager at Triple-A Toledo, Phil Nevin, said last summer that hitting was the least of his worries, which is why they were able to spend so much extra time every day working on outfield defense.
"There's not a level high enough where Nick's not going to hit," Nevin said in August. "He's going to hit."
Opportunity was the issue, and now Castellanos finally has it.
Castellanos is just the second Tigers player in the last 50 years to enjoy a two-hit game on Opening Day at age 22 or younger. Kirk Gibson was the last, homering and tripling in the 1980 opener. Now comes the next challenge, the daily grind.
It's the day-in, day-out routine, Castellanos' new manager says, that will test the youngster's mettle.
"Especially in this day and age of information in baseball, Major League pitchers, Major League scouts, Major League pitching coaches, they're going to find your weakness," Ausmus said. "And it becomes incumbent on the hitter to not offer at that weakness.
"Major League pitchers and coaching staffs, they will find your weakness. It's just how good you are at guarding against it. ... Make no mistake, there are very few Mike Trouts. Every young player is going to struggle at times. They're going to make mistakes. I think the key is to not look in the rearview mirror."
Castellanos went through a rehearsal of that last year in Toledo. He hit just .227 through the first week of May, then went on a tear that pushed his average over .300 by mid-June and into July. From there, Castellanos settled into the .270s by the home stretch, finishing at .274.
That was the International League. The Majors, Ausmus warned, is something else -- not simply for physical talent, but mental pressure.
"The hardest part, I think, is the mental aspect," Ausmus said. "You can struggle in the Minor Leagues. But all of a sudden, when you're playing for the Detroit Tigers and you're struggling while the team is supposed to be winning, it can be hard to cope with. You're reading about yourself in the paper, blogs are blowing you up and Twitter wants you out of the lineup. It's tough, mentally, on guys.
"Young players who are expected to do well put a lot of pressure on themselves. There are a lot of players who had exceptional talent but couldn't handle the rigors of Major League Baseball in the mental aspect."
Castellanos seems prepared for it, but he still has to experience it. If Opening Day was a test of nerves, the daily grind of the season will be a test of discipline.