The toss to first base took a chip out from the back of his protective helmet and stunned him for a moment but Cain stayed in the game with no ill effects.
"I'm fine, trust me," he said. "Everything is fine."
That's been Cain's theme song during Spring Training.
No wonder. Last year, which was to be his coming-out season as a Major League regular, he banged into the center-field wall at Oakland in the season's fifth game and came away with a left groin strain. While away on Minor League rehab, he tore his left hip flexor.
Finally, Cain got back on July 13 and played for two months before straining his right hamstring on Sept. 13. He missed the rest of the season.
"It was definitely very disappointing, having the spring that I did and starting off like that and getting hurt was definitely a big blow to me," he said. "But I stayed focused and bounced back to eventually get back on the field, although it took me until the All-Star break. I did pretty well and ended up getting hurt again so it was definitely a rough season for me."
So far this year the legs are fine.
"He's in a great shape," manager Ned Yost said. "He worked really hard on his legs this year. All aspects of it. He refined his gait, worked on his running, worked with a track coach. He really went the whole distance."
One possible challenge to Cain, hot prospect outfielder Wil Myers, was removed by the major trade with Tampa Bay. Cain still had to face competition from super-swift Jarrod Dyson, but Yost seems set on a healthy Cain.
During the winter, Cain worked with running coaches during visits to Kansas City and also with his personal strength coach, Tim Overman, at his Norman, Okla., home.
"I was kind of a long strider and it was more to allow my quads to work and other areas to work, to kind of balance out, so I wouldn't have to put all the force on my hamstrings," he said. "I was all hamstrings and putting more pressure on them. Throughout a long season, it's tough if they're working every single day like that. So [I wanted] to just kind of balance it out, use my quads, my hip flexors, other parts of my legs so I can last throughout the season."
Cain's legs obviously are important for ranging far and wide between left fielder Alex Gordon and right fielder Jeff Francoeur. All three of them are so proficient defensively that Yost mentions all three as possible Gold Glove winners -- something that Gordon has been the last two years and that Francoeur was in 2007 as well as being a finalist last year.
For Cain, Gold Glove time lies in the future.
His hitting at the Major League level has proved promising in what, so far, has been limited exposure. In a total of 110 games with Milwaukee and Kansas City, Cain's average is .281 with 32 extra-base hits and 45 RBIs. As a rookie with the Brewers in 2010, he batted .306.
Entering the last week of the Cactus League, Cain is 19-for-45, .422. Last Wednesday, he socked his first home run.
"He's an above-average defender in center field, he has very good power potential for a center fielder, he drives the ball from gap to gap, so we think he can be an above-average producer and defender in center," Yost said.
His speed has not translated into huge stolen base numbers as yet, although he was 10-for-10 in his attempts last year for the Royals. In 2010, he accumulated 33 steals in 37 tries for two Minor League teams and Milwaukee.
If Cain needed any tips, he could just cross the clubhouse and talk to the Royals' all-time leader in steals (612), Willie Wilson, who was in camp last week as a special instructor along with other Royals Hall of Famers, Dennis Leonard and John Mayberry.
"We talked a little bit in the dugout. He was talking about the things they used to do," Cain said. "Those guys could really play, so those are guys you could look up to and learn from."
Along with speed, Cain shares the same uniform number with Wilson.
"No. 6, I wear it proud," Cain said.