"I do what everybody else does," Kainer said. "If I get tired, I can pull myself out of a drill. They've given me control of my own body. They say if you're too tired or something is wrong, pull yourself out of a drill and take a breather."
Other than two NBA players, Sean Elliott and Alonzo Mourning, no major professional athletes have been known to resume their careers after having kidney transplants.
"One thing that keeps me going and working harder is knowing I have a chance to be a pioneer for the sport," Kainer said. "For a lot of children that start out with renal disease or kidney failure and have transplants at a young age, this would show them they can reach their goals and achieve dreams.
"You don't have to live a normal life just because someone tells you to. You can be extraordinary."
Kainer, a teammate of Reds' 2006 first-round pick Drew Stubbs at the Univ. of Texas, batted .364 with 66 RBIs last season for the Longhorns. He and Stubbs were named the squad's co-MVPs.
But while Kainer was having a terrific season on the field, a lifelong ailment finally caught up to him. He was born with a staph infection in one of his kidneys, a condition that wasn't realized until he came down with chicken pox at the age of 2. It led to chronic kidney failure, but he was able to lead a normal life while taking medication under the supervision of his physician, Dr. Eileen Brewer.
Stubbs was Kainer's roommate for three years at Texas and witnessed firsthand what his friend had to go through just to play baseball, let alone live his life.
"It was pretty remarkable, everything that he's been through and still be able to play at the level he has," Stubbs said. "Even before his transplant, it was a daily thing for him taking medication, and the highs and lows of energy levels from long days at the field because of it. It's an amazing thing that he was able to do everything that he did with that condition."
"It didn't really affect me on the field until this past year," Kainer explained. "I started to get tired and realized that my body was telling me something that wasn't good. It only happened in the last few weeks where my function dropped to about 13 percent."
Because of his condition, Kainer will not begin at the Rookie League level with the Reds right away as originally hoped. Cincinnati was aware of his situation and drafted him anyway.
"It was a decision based on his career at Texas," said Grant Griesser, the Reds assistant director of player development. "He was a really good hitter there. Once the medical clearance that he could do this was given by his surgeon, I think the scouting department figured this would be a good guy to get into the mix, get him down here and see what we can do with him."
Kainer was fortunate. He didn't have to go through kidney dialysis while waiting on an organ-donor-transplant list. His father, Ron, and his two younger brothers were tested and considered donor matches.
Since Ron was older than the brothers and also had the best tissue match as well, it was decided he would make the best donor. The transplant procedure was performed at Texas Children's Hospital in Houston. Aware of his career ambition, surgeons were able to place the new kidney behind the hip bone on Kainer's right side to give it extra protection from contact.
So far, recovery has been normal. To keep it that way, Kainer takes immune suppressant and anti-rejection medication twice a day -- at 9 a.m. and 9 p.m. -- which is something he'll have to do for the rest of his life.
"They really don't affect me on the field," Kainer said. "The only part is staying away from sick people, washing my hands and taking care of my body."
Meanwhile, the Reds are taking a patient and supportive approach. The organization has avoided any kind of timelines or goals for when Kainer might begin his pro career in games this season.
"It's a good situation for him to get into physical shape and start off slowly," Griesser said. "There's no hurry for him to make a team today. I think it's a matter of him easing into the rigors of pro baseball slowly and at his pace so that he feels comfortable with it. His body will dictate when he goes and if he can compete on a daily basis.
"We feel like there's no reason, once he gets his legs under him a little bit, he can't compete and do a good job here as a professional athlete."