Favorites lose, LAFC debuts, and youth was on display in Week 1

Toronto FC 0-2 Columbus: Champs stumble in opener - Via MLS (2:01)

Columbus Crew SC got the better of Toronto FC in the first MLS match of 2018, handing the reigning champions a surprising home defeat. (2:01)

With 10 games in the books and 20 teams showing themselves in league competition for the first time since 2017, the race is on to figure out Major League Soccer in the league's 23rd season. Despite the early nature of the returns and the limited evidence on hand, there are already themes emerging.

Here are three notable takeaways from the first weekend of the new campaign.

1. The favorites fall

It took just one round of matches for MLS to reteach a lesson we all somehow forget every offseason: The most predictable thing about the league is just how unpredictable it is.

Three of the presumed favorites to make runs deep into the playoffs fell on the opening weekend, with two of those clubs losing at home. With 33 games left, there's a better than good chance that Toronto FC, Atlanta United and the Seattle Sounders all meet the expectations put on them before the season began, but their losses spotlight the MLS's special flavor of chaos.

The reasons for the defending conference champions and the second-year darling of the league each losing in Week 1 are unique. Toronto FC played toe-to-toe with Columbus and couldn't click in front of net. Atlanta shipped four goals in Houston because of simple mistakes at the back and a gaping hole in defensive midfield. The Sounders rested key players ahead of a quarterfinal showdown against Chivas in the Champions League and proved dysfunctional in the attacking end.

Panic is only merited if the problems that revealed themselves in Week 1 can't be fixed quickly. Toronto figures to hit its stride, perhaps on the other side of the Champions League campaign, provided the roster stays healthy. The Sounders must adjust to life without Jordan Morris, something easier said than done.

Atlanta has the toughest challenge. Whatever plan the club thought would hold to cover for the loss of Carlos Carmona looks questionable.

2. Playing the kids

Amidst a national conversation over the place of young domestic players in MLS, Week 1 of the season delivered progress on that front.

In 2017, only one team, Real Salt Lake, started multiple teenage players in a match. On the opening weekend of 2018, both the Philadelphia Union and Portland Timbers lined up with more than one player under 20 on the field.

For the Union, that decision led to a 2-0 win over the Revolution and a first-ever goal for homegrown-signing Anthony Fontana. The 18-year-old rewarded head coach Jim Curtin's faith and gave credence to the possibility that young academy products are ready for the responsibility. Curtin also started 19-year-old Austin Trusty at center back in the clean sheet victory.

Portland's lineup with multiple teenagers featured one homegrown player, 19-year-old fullback Marco Farfan.

Elsewhere, D.C. United gave a debut to 18-year-old midfielder Chris Durkin, and Vancouver got a goal from their Canadian teenage sensation Alphonso Davies. It's far from anything we can call a trend, but if there's a small move toward playing young players made in the United States and Canada, that's a positive worth highlighting.

3. Dream debuts

Whether they be for rookies of several varieties, incoming foreign transfers new to the league in 2018, MLS veterans with new teams, or an entire club, debuts dominated the opening day of the season.

LAFC started life as an MLS team with a roster still under construction, but traveled to Seattle and scored a big road win. Nineteen-year-old Uruguayan DP Diego Rossi scored his first goal in MLS and will go into the record books as the club's first goal-scorer. Winning in one of the league's toughest environments is an impressive way to arrive on the scene.

The list of debutant goalscorers is long. NYCFC's South American signing Jesus Medina tallied his team's second goal in a win on the road in Kansas City. Unheralded offseason addition Stefano Pinho, a player who moved up from NASL, scored an important equalizer for Orlando City. Yamil Asad put his new team, D.C. United, up over Orlando City with his first goal for his new team. Kei Kamara scored on his debut for the Whitecaps, as did Ola Kamara for his first appearance in an LA Galaxy jersey.

The man Kamara replaced in Los Angeles, Gyasi Zardes, fired home an insurance goal in Columbus's impressive win on the road in Toronto.

Anthony Fontana's aforementioned goal for the Union in a win over New England makes the list, as does Darwin Ceren's for the fourth and final goal in Houston's domination of Atlanta.