The concussion, a subsequent neck surgery and recurring post-concussion symptoms were a constant partner of his, not only during the season but as he prepared in the offseason.
But Morneau comes to the Rockies armed with a two-year, $12.5 million contract, and a run of health that's more valuable than money. Not only did he play 154 games with the Twins and Pirates, but he had a winter during which he could simply prepare for baseball.
"When I felt like it was time to start hitting, I was able to do that without any second thoughts," Morneau said. "It seemed like everything was so regimented. I could take 15 swings off the tee to start. Then I could take 20 swings two days later.
"This winter, if I felt like going into the cage to hit, I could hit. If I wanted to hit on Saturday and Sunday, I could hit. If I wanted to go in there and work on stuff or take an extra round or extra three rounds, I was able to do that."
Before the concussion, Morneau batted .286 with 181 home runs, 679 RBIs and a .869 OPS, and was one of the best offensive forces in baseball. In the last three years of dealing with the aftermath of the head trauma, he has batted .256 with 40 home runs, 184 RBIs and a .725 OPS.
The left-handed-hitting Morneau was dangerous against all pitching early in his career. At the time of his injury, he had played 81 games in 2010 and had a .345 overall batting average and 1.055 OPS; and he was batting .325 with a .966 OPS against lefty pitchers.
In the last three years, he hit .206 with a .520 OPS against lefties.
Rockies manager Walt Weiss will give him shots against lefties, but the right-swinging Cuddyer can move from right field to first base. There's even a plan to give right-handed, power-hitting catcher Wilin Rosario time at first base.
But can Morneau earn the right to stay on the field against lefties? Maybe a full offseason of preparation could be what he needs to succeed.
"The worst thing you can feel as an athlete or a baseball player is feeling underprepared," he said. "When you're used to doing a certain amount of work in the winter and you get limited in that, that's when you come in and the preparation is what you need to feel.
"That's probably the biggest difference, coming in feeling like you can do the work that needs to be done to make it through the entire season."
The production began to return in Morneau's final days in a Twins uniform.
He hit .315 in May and .298 in June, although he had just two home runs by July 1. He slumped in July, going 17-for-107 (.175), but rebound to blast nine homers in August before being dealt to the Pirates. Morneau hit .260 with no home runs and three RBIs and turned out to be a complementary player rather than a force on a team that made the playoffs.
"It was a relief, but it was something that had been talked about for a couple of years -- whether I was going to be there [with the Twins] for the month of September," Morneau said. "It was an adjustment for someone who had been with one organization for as long as I was.
"Sometimes it feels like you're joining someone else's party, but they did a great job of welcoming me in and making me feel like I was part of that team. It was a great experience and let me know if I went somewhere else, it was going to be all right."
Morneau hit a combined .259 with 17 home runs and 77 RBIs. He replaces the retired Todd Helton, who, like Morneau, was coming off years of injury. Helton hit .249 with 15 homers and 61 RBIs last season.
"It'll be tough for anybody to fill those shoes, but we're doing it with a guy that's been a league MVP and has been an elite player in this league," Weiss said. "That ghost isn't overwhelming for someone like a Justin Morneau."
The Rockies looked at his 154 games played as his most impressive stat, figuring that a full season in one place -- with home games at Coors Field -- could allow him to approach his past numbers. Morneau must stay healthy and productive.
"It's something I really pride myself on, and it's something I was able to do early in my career," Morneau said. "I played 163 games one year. That's something you take pride in, be there for your team when they need you. Some of the stuff you can control, some you can't control. But for the manager to write your name somewhere in the middle of the lineup feels good, but you want to be productive, not just run out there every day."