When Mike Lowell took a high fastball from Joba Chamberlain and smashed it out of the park Sunday night, the moment represented a collision between the Ghost of Yankees Future and the Ghost of Yankees Could Have Been. It was also a potent signifier of how much has changed for the Yankees over the last 10 years.

Brian Cashman became the general manager of the Yankees on February 3, 1998. Within days, he consummated his first major deal, sending four prospects — one of them the former first round pick Eric Milton, then 22 — for All-Star second baseman Chuck Knoblauch. Cashman didn’t have to weigh too many other player acquisitions during the course of that season, as the Yankees went 114–48 and cruised to a championship. That winter, though, Cashman had to make his first major choice between youth and experience. Still learning, and not calling all his own shots, Cashman chose according to the Steinbrenner/Yankee way.

This early crucible was centered on third base and Lowell. The incumbent third baseman, Scott Brosius, had declared free agency. Brosius was a terrific fielder and inconsistent hitter who had happened to hit .300 AVG /.371 OBA /.472 SLG in a season where nearly everything touched by the Yankees was blessed. The year before, he had hit .203/.259/.317. In 1996 he had hit .304/.393/.516. Most hitters will hit within a fairly narrow range, but not Brosius. There was no way of knowing what kind of hitter he would be. But at 32, a dangerous age for a ballplayer of middling skills, he was more likely to be down again than up.

Also in 1998, Lowell had gotten his first cup of coffee in the majors, appearing with the Yankees on September 13. He had been a 20th-round draft pick in 1995, which meant that the Yankees, as well as every other team, thought of him as little more than filler for their minor league rosters. He did not prove the prediction wrong right away, but began a strengthening program in 1996 that would result in more power. The next year, as a 23-year-old playing in Double-A, he exploded, batting .344/.438/.561 with 15 home runs. Promoted to Triple-A halfway through the season, he batted .276/.348/.562 with another 15 home runs. In the winter of 1997, the Yankees traded pitcher Kenny Rogers for Brosius, who had largely been an everyday utility player for the Oakland A’s — he was almost always in the lineup, but often at a position other than third.

Lowell was blocked, but only temporarily, as Brosius’s contract had just a year to run. Returning to Triple-A Columbus during the 1998 season, Lowell had another strong season, batting .304/.351/.535 and knocking another 26 home runs. He had shown that his offensive improvement was for real. His defense was considered to be acceptable. The Yankees were, as ever, not a young team. Brosius was not young.

In the Steinbrenner era, the result could never have been in doubt. The Yankees gave Brosius a three-year contract in November of 1998. On February 1, 1999, just short of Cashman’s one-year anniversary, Lowell was dealt to the Florida Marlins for three pitching prospects, none of whom made an impact. Dealing Lowell made sense; with the signing of Brosius to a long-term deal, the Yankees had blocked Lowell for good, and at 24, his trade value would never be higher.

As it turned out, Brosius’s value would never be higher either. His bat was largely finished. In 1999, he hit .247/.307/.414. In 2000 he slumpedfurtherto.230/.299/.374. Finally, after a rebound year in which he hit .287/.343/.446 but missed a quarter of the season with injuries, he decided to quit while he was ahead.

Lowell’s Florida debut was delayed by a bout with testicular cancer. Surviving that, he rebuilt his strength and emerged as a solid if unspectacular offensive contributor in a very difficult ballpark. In 2003, he and Derek Lee were the offensive catalysts for the Marlins club that beat the Yankees in the World Series, with Lowell knocking 32 home runs during the regular season. New York’s third baseman in that series was the good fielding and weak hitting Aaron Boone. The Yankees were treading backward. Brosius’s replacement, Robin Ventura, aged too quickly, as did his platoon partner, Todd Zeile. Trying to fill the position, the Yankees made a desperate deal at the trading deadline, giving away a well-thought-of pitching prospect at the time, Brandon Claussen.

In retrospect, it appears that the Yankees were simply traveling the convoluted road that would lead to Alex Rodriguez, but that was not predestined. If not for a contract snag, Rodriguez would today be with the Red Sox. Good luck rescued the Yankees from their initial decision to choose Brosius over Lowell (though the cost was high in resources spent), as well as other similarly incorrect lessons: When the Yankees won two World Series in spite of Brosius’s decline, it seemed to inculcate the idea that the team could make the same sloppy decisions it always had, favoring mediocre veterans over promising youth, and still prosper. With no championships since 2000 and a recent sea change in the way they treat young players, it seems safe to say the Yankees know better now.

Meanwhile, Lowell is with Boston, enjoying his finest season since 2003. He will be a free agent at the end of the year. Should Rodriguez opt out of his contract, it’s quite possible that the Yankees would pursue Lowell to replace him. But Lowell is 33 now, well into baseball old age. It would be sad if those who signed Brosius were condemned to repeat him.

Mr. Goldman writes the Pinstriped Bible for yesnetwork.com and is the author of “Forging Genius,” a biography of Casey Stengel.