Rosario set a Rockies rookie record with 28 home runs, led National League rookies with a .530 slugging percentage and drove in the more runs than any Rockies catcher in a season, with 71.
The question now is whether he and the Rockies will be able to sing joyfully when he puts on the catching gear.
Rosario's 21 passed balls and 13 errors are figures recited as often as his power numbers. Granted, the young staff was at or near the bottom in many significant categories, but the 94 wild pitches -- 19 more than the next-wildest staff -- ended up reflecting on Rosario.
It led to a winter of focus on defense, including a stint in winter ball in the Dominican Republic and drill work at the Rockies' complex there. Jerry Weinstein, the Rockies' catching instructor, even made a trip to the Dominican Republic to evaluate and instruct. But will it lead to improvement?
"It's like a test in school," Rosario said. "If you're a student all year, you're going to pass, right? That's what I did in the winter -- study."
In all fairness, the work can't be considered exactly remedial. Rosario was limited to 73 games in 2010 in Double-A because of an injury to his right knee that required surgery. He played at that same level in 2011 before making his big league debut, and his hitting last spring forced the Rockies to jump him past Triple-A last year. That move left the club trying to teach him on the run, and the errors and passed balls flowed.
The degree to which the problems affected Rosario is debatable.
There was the embarrassing afternoon in Philadelphia when he committed four passed balls and was threatened by then-manager Jim Tracy with a benching, only to have to be thrown back into action because of Ramon Hernandez's hamstring injury -- his second injury of the season. There were also strange games in which he played third base and first base, with poor results.
But if his problems on defense were weighing on him, it didn't affect his hitting.
"Either he is a great actor or he is a very even, self-confident personality and understands the reality of the environment and he's able to control those," Weinstein said. "In my opinion, it's the latter."
The original plan last year was to play Rosario occasionally and work on fundamentals between starts. But Hernandez's strained left hand early in the season meant Rosario had to be taught on the run -- but sometimes pregame work on handling pitches inside to batters, blocking pitches at his feet or correcting stance habits left him unable to react freely during games.
Instruction is being simplified. He and the other catchers block balls every day. While catching bullpen sessions, they work on the transfer of the ball from the glove to the free hand. (For all the errors, by the way, Rosario threw out a healthy 32 percent of would-be basestealers.)
The Rockies consider Rosario an exceptional athlete, and not overcoaching such a talent is a tenant of coaching. The test will be when he has his first miscue or the inevitable slump.
"I am kind of like the guard rails on the freeway," Weinstein said. "But the reality is, the player taken personal responsibility, and making his own adjustments is far better than somebody on the outside looking in, and taking care of that person to where they become codependent on that coach or manager."
History suggests that a season filled with passed balls doesn't kill a career. Ted Simmons appeared in eight All-Star Games in a career that ran from 1968 to 1988, but he led his league in passed balls three times -– with 28 one year and 25 another. Benito Santiago had seasons in which he allowed 23 and 22 passed balls. Former Red Sox captain Jason Varitek had 25 in 1999. Young staffs and the presence of a knuckleballer are conditions that can drive up such figures.
New manager Walt Weiss believes that Rosario's struggles last year are a result of his abrupt entry into regular big league playing time with a young pitching staff.
"He's got the skills to be a frontline catcher, and he's got the all-around skills to be a star in this game," Weiss said.
The Rockies also downplayed a couple of physical issues that affected Rosario, but there was one they had to acknowledge. On June 20 he caught a spike in the dirt behind home plate in San Diego, fell awkwardly and had to leave the game with a sprained left ankle. He still played regularly, so the injury never healed.
Another key impediment was not discussed. The surgery he underwent in 2010 cost Rosario -- already built for lower-body explosion but not for extreme flexibility -- the ability to comfortably maintain a low stance.
That stance isn't necessarily bad. Working from a similar position, all the Cardinals' Yadier Molina does is win Rawlings Gold Glove Awards -- the last six. But Rosario had a difficult time staying low enough to block pitches, and setting up on the corners and reaching pitches off the plate were challenges.
"At some point -- if you ask me, I say I don't know -- I changed my stance, to a 75-25 angle," said Rosario, who is doing preventive flexibility work under the care of strength and conditioning coach Brian Jordan and head athletic trainer Keith Dugger. "Now [with the tips of my toes at or about even], I can see the ball better, and I feel better."
Left-hander Jeff Francis said that the Rockies need for Rosario to be comfortable and competent in all aspects of the game. After Francis' first Spring Training bullpen session on Monday, he made it a point to offer encouragement and information to Rosario.
"I'm impressed by what we saw last year, but one thing for sure is, he can help this team more behind the plate than at the plate," Francis said. "We take it on ourselves as pitchers to make him better, as well."
Having done the requisite homework, Rosario is eager to do what everyone wants to do when school is out -- have fun.
"I'm not going to worry about anything," he said. "I'm not going to worry about if I miss or if I'm wrong somewhere. I just want to go out and play."