That seems to be particularly true when it comes to the potential of players in the Minor Leagues. Some -- can't-miss prospects Bryce Harper and Mike Trout come to mind -- lived up to their big league billing right away and have already become legends. Some never pan out.
It's simply impossible to really know who will hit big and who won't. And that uncertainty, of course, makes it incredibly fun to talk about in the years before everyone knows their names.
Saturday marks the much-anticipated release of MLB Pipeline's preseason Top 100 Prospects list, and you can watch the one-hour show on MLB Network and MLB.com at 8 p.m. ET. In other words, it's an ideal Throwback Thursday to recall previous years' lists and see how some of baseball's best players were ranked way back when.
Here's a look back at how we described five current stars before they made it big:
Nolan Arenado, 3B, Rockies: Arenado has become one of baseball's best all-around players. He's a perennial Silver Slugger and an even more sure bet as a yearly Gold Glove winner. That's why it's interesting to see that his fielding was the part of his game that was in question when he was a youngster.
"There was concern about his defense at third, but he's worked to improve, and those worries are gone," read MLB.com's scouting report of him on the 2012 Prospect Watch list, where Arenado was ranked 27th overall after being selected by Colorado in the second round of the 2009 Draft. "It might not be too long before Arenado is spotted in Coors Field."
Good call. Arenado, who turns 26 in April, continues to work to improve. His debut in the Major Leagues came as predicted by MLB.com, in 2013, and he's won Gold Gloves in all four of his Major League seasons. It might only be a matter of time before he wins an MVP honor to add to all those shiny mitts.
Mookie Betts, RF, Red Sox: Betts was a fifth-round pick by Boston in 2011 and overlooked in the team's system for a bit. Then his pure, mind-blowing athleticism came to fruition with blinding speed, Betts, who was originally expected to be a second baseman, rocketed to the big leagues, switched to the outfield and he almost won the American League MVP award last year after slashing .318/.363/.534 with 31 home runs, 113 RBIs, 26 steals, 42 doubles, 122 runs and 214 hits.
Betts wasn't on the Top 100 Prospects radar in 2013. In fact, he was ranked 16th in the Boston system. But the scouting report showed that his physical gifts were more than well-known, which is why Betts began the 2014 season at No. 62 on the Top 100.
"A premium athlete coming out of the Tennessee high school ranks, Betts got an above-slot deal to sign in 2011," it read. "The undersized middle infielder has some surprising strength and was showing more extra-base power during his full-season debut in 2012. He understands, though, that his job is to get on base and use his speed on the basepaths. … He profiles as a top-of-the-order type, especially if he can continue to show he can make consistent hard contact at the plate."
"He has the chance to be an outstanding shortstop who excels in all facets of the game," his 2012 Pipeline scouting report read. "Lindor has a very advanced approach at the plate as a switch-hitter, and should hit for average and power from both sides. He gets on base and is a heady runner. There's no question about his defensive ability, with a plus arm and range. While Lindor is a teenager who spent the year at Class A Lake County, don't be shocked if he's able to move faster than most prepsters."
We're not surprised.
Anthony Rizzo, 1B, Cubs: Rizzo had already beaten cancer and was a San Diego Padres' farmhand when profiled in the 2011 Prospect Watch. Rizzo, who was taken by the Red Sox in the sixth round of the 2007 Draft, was already accomplished at Triple-A with not a lot left to prove at the plate and thus finished the season ranked 18th overall.
"Rizzo's bat continues to develop as he moves further away from overcoming Hodgkin's lymphoma," the MLB.com scouting report read. "He's exactly what you want from a first baseman, with plenty of power from his left-handed bat. There is some swing-and-miss to his game, but he should continue to improve his plate discipline. He needs to improve against lefties, and it looked like he was making strides with that as the season got underway. He's a very good defender at first base as well and was just 21 years old for most of the 2011 season."
The report ultimately nailed its upside potential projection of Rizzo as "a very good power hitter and run producer in the middle of a big league lineup."
Rizzo, 27, landed on the Cubs in 2012, has averaged 30 homers and 92 RBIs over the last four seasons and had his best year last year, when he slashed .292/.385/.544 with 32 homers and 109 RBIs and won his first Gold Glove as the Cubs won the World Series for the first time in 108 years.
"A hard thrower, Syndergaard is much more than arm strength," the 2012 report read. "The 2010 supplemental first-rounder does get his fastball into the upper 90s and commands it fairly well. His power breaking ball has the chance to be above-average as it becomes more consistent, and his changeup should also be above average or better. With a strong and projectable frame, he has all the tools to be a frontline starter in the future."
It happened in 2015, of course, with Syndergaard solidifying a dynamic young Mets rotation that made it all the way to the World Series. Now he looks like a threat to pitch a no-hitter every time he strides atop a mound.
Doug Miller is a reporter for MLB.com. Follow him on Twitter @DougMillerMLB. This story was not subject to the approval of Major League Baseball or its clubs.