"As soon as you see some kid who's bigger than the others, or can hit the ball farther than the other kids, everyone starts doubting," Perez says.
First it was allegations steroids abuse, reports CBS' Russ Mitchell. Now an even more elusive threat — human growth hormone or HGH.
"It's really frightening," Perez says.
The fears are realized by Major League pitcher Jason Grimsley's admission in a federal affidavit to using the banned drug, along with dozens of other players.
"Baseball now — if it didn't know before — knows it has a huge HGH problem on its hands," says baseball writer Tom Verducci.
Natural HGH is produced by the pituitary gland to stimulate normal development and growth. Athletes looking for an edge inject high doses of synthetic HGH to increase muscle, shed fat and speed recuperation, but there are some very dangerous side effects.
"They develop diabetes, hypertension, vascular disease, colon cancer," says Dr. Gary Wadler, an anti-doping specialist.
Since HGH is virtually undetectable in urine tests, none of the four major American sports leagues test for it.
"We have become so much better at the detection of anabolic steroids that the marketplace has shifted," Wadler says.
That shift is obvious on the Internet where this search for Human Growth Hormone resulted in more than 4 million hits. HGH has become a mail-order business.
"We really don't have a handle on who's using and how much they are using," says Dr. Gary Green, who advises Major League Baseball on its drug policy. "We know we are one step behind — we don't want to be two steps behind."
So scientists at a University of California lab are racing to develop a urine test for HGH. But critics like Wadler worry that could take a decade or more.
"The quantity of human growth hormone in urine is exquisitely small and that's just one of the problems that the research scientists have to deal with," Wadler says.
The International Olympic Committee uses a blood test for HGH. But it's not definitive, requires frequent testing, and few believe American pro-players will ever agree to it.
"Especially if you can't convince them that the blood test you take from the sample is 100 percent reliable," Verducci says.
The high cost of HGH — about $3000 a kit — has largely kept it away from young athletes. But that too may soon change. The FDA just approved a generic form of the drug that some fear could make it more affordable than ever.
"We should not ignore what we learned about anabolic steroids in high schools," says Wadler. "But we should learn from that and work to prevent the very same thing from happening with human growth hormone where the risks perhaps are even greater."