It's hard to imagine how or when, but somebody probably will come along and hit home runs like Barry Bonds used to hit 'em.
A base-stealer the likes of Rickey Henderson, on the other hand, is probably something that nobody will ever see again.
When Henderson debuted for the Oakland Athletics on June 24, 1979, Lou Brock held the records for stolen bases in a season (118 in 1974) and in a career (921 as of that date). Henderson broke the former with 130 swipes in 1982, and he later surpassed Brock's career total in 1991 on his way to a whopping 1,406 thefts over 25 seasons.
That Henderson was able to steal so many bases is largely a testament to his rare blend of speed and on-base acumen. Regarding the latter, only he and Ty Cobb can claim to have taken as many as 13,000 plate appearances and posted an on-base percentage over .400.
Yet Henderson's stolen base records are also a product of the era in which he spent his prime. Though stolen bases have mostly been out of fashion ever since Babe Ruth popularized the home run in the 1920s, they were suddenly back in fashion from the late 1970s through the early 1990s:
This was a byproduct of the league's home run rate taking a break from its longstanding upward trend. In lieu of hitting the ball over the fence, getting 'em, getting 'em over and getting 'em in took hold as the default mode of offense for most clubs. Stealing bases was a key part of the equation.
Though Henderson was the base-stealing star of this era, he wasn't the only one. Vince Coleman matched him with three seasons of 100 stolen bases, and 29 other players notched at least one 50-steal season.
But ever since the home run began a lasting come back in 1994, the stolen base has once again fallen out of favor. Only eight players stole as many as 50 bases in a season throughout the 2010s, and nobody has done it since Billy Hamilton and Dee Gordon in 2017.
If the lines in the graph above are any indication, stolen bases won't become popular again until the home run rate goes down and stays down. That's a hard thing to count on, and a new-age Henderson might not necessarily arise even if it happens.
Before a hitter can steal a base, he must first get on base. Henderson was obviously very good at that, but it was comparatively easy to get on base during his heyday. In the 1980s alone, hitters got on base at a .324 clip. Throughout the 2010s, the league's OBP was only .320.
The big difference? Strikeouts.
The strikeout rate for 2019 (23.0 percent) was nearly twice what it was in 1980 (12.5 percent). And there seems to be no reversing this trend, as the league has been setting new strikeout records annually since 2008.
Perhaps that trend will finally reverse if the home run rate also reverses, in which case hitters might de-emphasize swinging for the fences in favor of merely making contact. But even then, they'll still have their work cut out for them because pitchers will presumably still be throwing hard fastballs and aggressively using their secondary pitches.
Still another question for this hypothetical low-homer environment is how long the leashes on base-stealers would be.
After all, stolen bases haven't gone away just because the rising strikeout rate has made it more difficult to get on base. Teams are also taking fewer chances than they did in Henderson's day:
Granted, this is partly because hitters don't simply go to first base as often when they do get on. In the 1980s, walks, singles and hit-by-pitches accounted for 79 percent of all on-base events. In the 2010s, just 76 percent.
This is also, however, the inevitable result of a wider reassessment of the risk and reward of stolen bases.
Ironically, the most notable of Henderson's many former teams was at the center of this. Oakland's disdain for stolen bases during the 2002 season was well-chronicled in Moneyball, wherein third base coach Ron Washington told author Michael Lewis: "There's a rule on this club. It's OK if you get it. If you don't, you got hell to pay."
For what it's worth, that rule actually worked as intended. Though the 2002 A's finished dead last with 46 total stolen bases, they stole them with an above-average 70 percent success rate.
Pretty much all of Major League Baseball has since bought into that proof of concept. Even though stolen base attempts are way down, the leaguewide success rate has increased from 68 percent in 2002 to 73 percent in 2019.
To be sure, it helps that catchers don't throw many runners out anymore. The league's 26.7 caught-stealing percentage in 2019 was one of the worst in history. And that's almost certainly not just a function of base-stealers getting more efficient.
As the stolen bases have declined and appreciation for skills like game calling and pitch framing has risen, strong arms have become less of a necessity and more of a bonus for catchers. Otherwise, guys like Kenley Jansen, Josh Donaldson and Bryce Harper might still be catching today.
However, pitch framing will become a relic once MLB finally implements an automated strike zone. Catchers' only duties then will be calling pitches and controlling the running game, which could convince some teams that there's an edge to be gained by bringing back the strong-armed catcher. That, in turn, would add another element of risk for would-be base thieves.
Ultimately, it's hard to see the conditions that helped enable Henderson's stolen base records ever taking hold of Major League Baseball again. Even if the way is paved by home runs suddenly vanishing, strikeouts and a generally more cautious approach to stolen bases should keep his marks safe.
In other words, what Henderson said in 1991 about being the "greatest of all time" was both a statement of fact and a prophecy.