Past performance is no guarantee of future results.

It’s a caveat that anyone who’s ever invested or even thought about investing in the stock market has heard. When it comes to investing in baseball players, the same caveat applies. That’s why last year, when Bryce Harper followed up his all-world 2015 season with an all-what-the-heck 2016, questions about his long-term value started to surface.

At the end of 2015, there was talk about how when Harper hits free agency in the fall of 2018, he could become MLB’s first $400 million man. Maybe even half a billion if the planets were aligned just so. And for good reason. After all, the Washington Nationals superstar was just finishing up a season for the ages, one in which the former first overall pick came into his own, hitting .330 with 42 home runs and posting a 9.9 WAR en route to becoming the youngest unanimous MVP ever. It’s that last part -- the young part -- that had everybody projecting a historic haul come free agency. Because how often does an MVP-caliber player like Harper, a man-child who debuted with the Nationals at 19 years old, hit the open market in his mid-20s with a seemingly infinite number of good years left in him? Pretty much never.

Fast-forward to February 2016, when the reigning MVP sat in the first base dugout at spring training and, squinting into the bright Florida sun, said the following to reporters: "Everybody says the sky’s the limit. But we’ve been on the moon." On the one hand, Harper might have been talking about on-field production and implying that his huge 2015 campaign was just the tip of the iceberg. Then again, maybe his moon talk had more to do with his future earning potential. But a funny thing happened on the way to free agency.

With Bryce Harper set to be 26 when he hits free agency, one GM suggested that he could command a contract of 15 years at $40 million per season. Brad Mills-USA TODAY Sports

After starting off strong in 2016 and being named National League Player of the Month for April, Harper fell off a cliff. Following an early May series at Wrigley Field in which the Cubs walked him approximately 4,000 times, he appeared to grow impatient at the plate and started pressing. After he missed five August games with a neck problem, reports surfaced that Harper hadn’t been 100 percent healthy for much of the season. He finished the year with a .243 average, nearly 100 points lower than his 2015 clip, and posted a 1.6 WAR that represented the largest drop-off ever by a reigning MVP. Whether it was the Wrigley Field walk-a-thon, his health or simply the growing pains that come with being a 23-year-old big leaguer, suddenly Harper didn’t seem like such a sure thing. Suddenly, that $400 million seemed like crazy talk.

But two months into the 2017 season, the 24-year-old slugger is once again setting the world on fire. Through the end of May, Harper ranked among the top five in the NL in batting (.328), homers (15), RBIs (43), runs (44), slugging (.655) and OPS (1.093), and he was one of the main reasons the Nationals were sitting atop the NL East with the second-best record in baseball. In short, he looks a whole lot like his MVP self, which raises the following question: When it comes to Harper’s long-term value, just how much does last season matter in the minds of front-office folks?

"Forgotten," an American League general manager said of Harper’s 2016 tumble. "Last year, he still had the classic walk rate, so you know things were happening positively for him, and you know there was something happening on the injury front. For two of the last three years, if he hasn’t been the best player in the National League, he’s certainly on the short list. He’s one of the best players in the world. He’s one of the youngest players in baseball, and he’s one of the most accomplished."

Before long, he’ll be one of the wealthiest. Said the GM: "He is going to get paid. Like, paid paid."

Relative to his tenure, Harper’s already getting "paid paid." On May 13, he and the Nationals agreed to terms on a one-year deal worth $21.625 million for the 2018 season, the final year of his current contract. The deal was an anomaly on two counts. First, players who are eligible for arbitration typically don’t have their contract situations settled so far in advance; those negotiations usually take place after the season. Second, and more significant, the pact set a record for the largest one-year contract ever given to an arbitration-eligible player. The previous record belonged to pitcher David Price, who inked a one-year, $19.75 million deal with the Tigers for 2015. The record holder before Price? That’d be hurler Max Scherzer, who received $15.525 million (also from Detroit) for the 2014 season. It’s worth noting that both Price (seven years, $217 million) and Scherzer (seven years, $210 million) went on to ink massive free-agent deals the year after those record-setting contracts. In other words, in a negotiating environment where precedent typically takes precedence, it would appear that Harper’s well on his way to a profound payday. But just how profound?

“Four hundred million is light,” the GM said. “It's going to be more than that. If you could sign him to a 15-year contract, you do it. I would say something in the range of $35 million a year, maybe closer to the high 30s. It could approach 40 million dollars a year.”

"He is going to get paid. Like, paid paid." American League GM

Those numbers aren’t coming out of thin air. Based on average annual value, the highest-paid player in today’s game is right-hander Zack Greinke, whose contract with the Diamondbacks earns him better than $34 million per season. On the one hand, Harper’s not a pitcher like Greinke (or Price or Scherzer). On the other hand, he (A) already has one MVP on his résumé, (B) is in the conversation for another, (C) hasn’t even hit his prime yet, and (D) is repped by super-agent Scott Boras. All of which suggests that the idea of Harper becoming the highest-paid player in the game isn’t a far-fetched one. As for total contract value, that depends on how long both sides are willing to commit.

Given that Giancarlo Stanton is the only current MLB player with a deal that spans more than a decade (13 years, $325 million), the aforementioned 15-year pact seems outrageous -- until you consider that Harper will have just turned 26 when the bidding for him begins. A 15-year agreement would take him through his age-40 season, the same age Miguel Cabrera will be when his eight-year, $248 million deal with Detroit expires. So really, it’s just a question of how long Harper wants to be locked up. If it’s for only 10 years (Troy Tulowitzki, Joey Votto, Robinson Cano and Albert Pujols are all on decade deals), then his deal could fall in the $350-400 million range. If, however, he’s open to the idea of a Stanton-sized term (or longer), then simple multiplication says Harper could be looking at $500 million or even more, depending on how the market plays out.

“When you’re making a presentation to ownership,” another American League GM said, “the question you expect to get is, once we make this the highest-paid player ever, how much higher than the highest do we have to go?” More than likely, the answer will be dictated by the laws of supply and demand.

The Yankees, Phillies and Dodgers are all expected to be in the mix. The Nationals -- as suggested by the record-breaking deal they gave Harper last month -- will do everything in their power to keep the face of the franchise in D.C. There’s bound to be a surprise suitor or two as well. “Some owners will bow out,” the second GM said, “because they think becoming the highest-paid player should be sufficient. Having to go 10, 20, 30 percent above that is going to become increasingly challenging for people who are uber-successful businessmen.”

Although price might be a sticking point for such magnates, two months into the 2017 season, it appears that past performance is not.

“When you’re talking about a guy who’s under 25,” the first GM said, “a year ago is ancient news.”