Just days before acquiring first-base prospect Anthony Rizzo from the Padres, Cubs president Theo Epstein appeared on Chicago radio and reiterated his support for Bryan LaHair.

"Bryan LaHair is our first baseman," said Epstein. "I don't believe in the concept of 4-A players. The guy can hit."

The concept of the Quad-A hitter is as old as the minor leagues. For every player that figures things out late, like Nelson Cruz, or even non-stars like Jorge Cantu, there are plenty of Triple-A sluggers like Kila Ka'aihue, Brad Eldred, Calvin Pickering, and Sam Horn, who put up crazy numbers, but never have big-league careers. Are they Quad-A hitters? Does such a thing even exist? Are Quad-A hitters simply players who never got the right time to showcase, or got cold at the wrong time and never received the opportunity to un-bury themselves? Or are some players simply unable to handle the job? I talked to several people in the industry to get their answer.

While not everyone even agrees on the existence of such players, there were three main ways a player can earn that label.

He has to Really Hit
One National League executive doesn't really believe in the concept of the Quad-A hitter. �I don't think it's that 4-A type guys can't hit major league pitching, so much as it's 4-A type guys have no value besides their bat,� he explained. �If you are a bad first baseman, or left fielder, or designated hitter, just being an average big-league hitter doesn't really cut it, so you better hit the moment you get an opportunity or the industry moves on to someone else.�

An American League scouting executive agreed. �If a guy is a strong defender, certain teams can give him a lengthier trial, but if hitting is all they can potentially do, the game doesn't allow that kind of time. If his game beyond the bat is mediocre or worse, it often doesn't allow the club to give the player the time needed for the talent to manifest.�

There is no universal timetable for talent. For some, it can be a month of two. For others, like Royals outfielder Alex Gordon, it can take years. Adjustments are necessary, and those bring in factors players never see in the minor leagues.

An Inability to Make Adjustments
For more than one industry insider, the biggest challenge of jumping from the minors to the majors is not about the opponents on the field, but the opponents in the stands�especially the ones behind home plate. �The minor leagues are about player development, and the major leagues are about winning,� explains another National League exec. �The minor leagues don't have advance scouts. Advance scouts are there to take apart hitters and exploit weaknesses. The players that can't adjust to that are the ones that end up 4-A hitters.�

An American League scouting executive agreed. �Miguel Cabrera and Justin Upton don't grow on trees,� he said. �Everyone else that is human is going to go through an adjustment period.�

The executive pointed out some players who took extra time to develop. �Nelson Cruz bounced all over, and then exaggerated his stance and hit in the middle of a World Series lineup. Mike Morse transformed into a more physical player, made some changes in his set up, and hit 30 home runs. Any team in baseball could have had Carlos Pena, but he didn't become the 40-home-run guy people thought he would be all along until he was 29 and on his fifth team.

�Some guys never get it, but while all 30 teams want the best and the brightest, we're giving up on players too soon sometimes.�

For a veteran National League scout, the inability to make adjustments can lead to additional issues when it comes to makeup. �At first, it's not about the lights, or the two decks in the stadium, or the crowd,� the scout insisted. �It's about the breaking balls and the depth of arsenals and the command. It's an inability to adjust that comes first, but that can lead to the mental stuff where players get overwhelmed, and the 4-A label just becomes a self-fulfilling prophecy.�

Still, for the most part, the industry believes that there are some players who will never make the adjustments, and there are some scouting clues as to who those players will be.

A Lack of Talent
While we can list plenty of players who shed the Quad-A label and became productive big-league hitters, they're still the minority, so talent does play some role.

�Quad-A hitters definitely exist,� said an American League assistant general manager. �There's definitely enough of a gap to allow some skill sets to exploit Triple-A pitching and not adjust. They can be crushing average fastballs at Triple-A.�

An American League scout echoed that sentiment. �Some of these guys are getting six real mistakes to crush a week at Triple-A,� he said. �In the big leagues, he gets one or two a month.�

An American League scouting executive explained that bat speed often separates the wheat from the chaff. �Many of these players have more strength than bat speed,� he explained. �They have to cheat to get to pitches, and those extra two ticks of velocity in the big leagues kill them.�

A National League scout gave a real-world example. �I saw Dallas McPherson going off in 2011, slugging .505 at Triple-A Charlotte, which he's done for years,� he said. �But in looking at him, he was still very exploitable. He really had to cheat to catch up, His setup is scary: open, and way off the plate. That leaves him vulnerable inside, and if I can see that, you know big-league pitchers are going to see that.�

Still, identifying the players who will buck convention remains one of the game�s great mysteries. �Yes, there are guys who just put it together from time to time, but they're in the minority,� said a National League front-office executive. �Usually, if a guy fails and reaches a certain age, it's just not going to happen.�

An American League executive shares the frustration. �There's no rhyme or reason to it. Whether you are projecting with scouting or sabermetrics, you still need a touch of Nostradamus. The hardest part of the game is getting over the Triple-A hump, and it's still very hard for us to predict who is going to get over it.�

A version of this story originally appeared on�ESPN Insider�Insider.