"There's guys who have come on the news and I thought, 'People aren't going to believe him,'" Nieto said in an interview with MLB.com.
"I didn't believe them. Now, I'm in their shoes. I'll be an example right now, not in the right way, but if they're going to go to the gym or a GNC, hopefully they won't go and buy something if it's not certified."
According to Nieto, he got in the habit of grabbing protein shakes and liquid supplements like that from the refrigerator in his local gym. He never suspected that they would cause him to land in the situation he's currently facing.
"That's what happened here," Nieto explained. "Every time I went to the gym, I'd grab any protein shake before I worked out, not thinking that one day I'd fail a drug test."
Nieto doesn't think he's blameless in all of this. He admits he was careless not to check the ingredients of what he took or to ensure that what he took was officially certified as being OK according to baseball's rules.
"Every time we go to Spring Training, we have our agents and trainers make sure supplements we take are certified," Nieto said. "A lot of us listen and we think we won't fail a test because of a protein shake or something we take at a local gym.
"I never asked, which was dumb on my part. That's what my farm director said -- that I need to be smarter than that. They specifically tell us at instructs to make sure. That was dumb on my part. Being young and stubborn, I didn't think it could have something in it that would trigger a test."
Nieto came out of the Florida high school powerhouse American Heritage, which has produced a handful of top Draft prospects. The Nationals gave him an above-slot $376,000 to sign him.
The switch-hitter's career had begun somewhat slowly, as he spent his first two summers in the Gulf Coast League. He moved up to full-season Hagerstown in the South Atlantic League in 2010, playing in just 60 games and hitting .195.
The 2011 season was shaping up to be a big one for the catcher, one in which he needed to show progress and the ability to stay on the field for an entire year. Instead, he'll have to wait 50 games from the start of the season to get going and erase the sluggish start.
"It's a mistake, it's disappointing," Nieto said. "All that work I was putting in, now I have to work twice as hard to get to where I was trying to get."
Nieto also understands it's more than his ability to show he can be a professional catcher that will need to be proven. A positive test, no matter the cause or the player's explanation, carries with it a certain stigma. Repairing that will be extremely difficult. Nieto is prepared for people to be skeptical, at best. But he's willing to work on that, starting with being a cautionary tale and talking to those at his former high school.
"This can make it seem like I'm a bad person," Nieto said. "It's an honest mistake. It could happen to anyone. For players in the Minor Leagues, guys that are coming up from high school or college, don't make the same mistake I made. If you're going to take something, do it through your trainer or a coach -- someone you trust. Make sure it's certified. It's not a good place to be in. A lot of things are going to be said about me for a lot of reasons.
"I'm going to talk to them and let them know they have to be more careful [about] what they put in their bodies. I didn't take what was told to me and to every player, I didn't take it as seriously as I should've. Now I see why -- to make sure they're certified. They go through a certain test to make sure they're clean for us. They're not messing around. It could've been different. I've already learned my lesson."