Even before David Beckham swapped Madrid for Los Angeles, MLS has harbored a reputation as a “retirement league.” The notion is well-worn in banter circles. It’s tired, and also at least a little bit true.

Robbie Keane. Kaká. David Villa. Andrea Pirlo. Didier Drogba. Wayne Rooney. Zlatan Ibrahimović. All of them – and many others – enjoyed late-career stops in the United States. Today, three of the 11 players named to Fifa’s Dream Team after the 2014 World Cup play in the league: Lionel Messi (Inter Miami), Thomas Müller (Vancouver Whitecaps) and James Rodríguez (Minnesota United). When Son Heung-min (33 years old) arrived in Los Angeles after his decade with Tottenham, he reunited with longtime Spurs teammate Hugo Lloris (39), and ensured derby days against the LA Galaxy’s Marco Reus (36).

None of these players, though, are the bellwether. If that distinction belongs to anyone, it may just be 17-year-old Red Bull New York starlet Julian Hall; currently tied atop the MLS golden boot standings, and an invaluable part of one of the feelgood stories early in this season.

Hall has been electric in the first two weeks, which also happen to be the first two weeks of...