PORTLAND, Ore. — If there is a single unifying theme at the dawn of another Major League Soccer season, it is expansion — in regard to Atlanta United and Minnesota United, the teams making their debuts this weekend, and for the young league as a whole, moving forward.

22 and Counting

M.L.S. kicked its 22nd season Friday night at Providence Park in Portland, Ore., with 22 teams. It is not stopping there.

The league will add a second Los Angeles club next season, Los Angeles F.C., and a 24th spot is being held for David Beckham’s still-hypothetical Miami franchise. The league plans to keep going until it hits 28 teams — Commissioner Don Garber referred to that as the “final landscape” in a phone interview this week — and last month the league received official expansion bids from 12 cities for the final four spots.

Whether continued expansion is the best path forward for the league is a topic of debate. Garber plays down concerns about diluting a still-developing talent pool, but there is little doubt that M.L.S. still has some distance to go on that front to catch up to the biggest European leagues.