Maybe the larger lesson of this opening month is that the National League may be just as wide open as it appears. That's good news for the Diamondbacks and Rockies, for the Pirates and Brewers and perhaps others.
Actually, it's good news for all of us. Few things in baseball are better than a chaotic September pennant race. And because everything is connected to every other little thing, the division races could play out way different than we thought.
If the Mets and Giants aren't as strong as we projected them to be, and other teams are a bit stronger, that tightens all the races. Sure, it's still early. On the other hand, who expected to see the Diamondbacks and Rockies in first place, the Mets and Giants in last? That change could be symbolic of a larger shift.
On Opening Day, the Nationals, Cubs and Dodgers were solid favorites to win their divisions. They may still do exactly that, but the big picture suddenly has a bit less focus.
Let's look at the division favorites.
1. Nationals
This may be the NL's best team. But it's not perfect. Washington's relievers have stumbled out of the game, compiling a 5.70 ERA, the third highest in the Major Leagues. Center fielder Adam Eaton's season-ending knee injury weakens the league's deepest lineup. All this is relative. The Nats are going to win the NL East, and they will try again in October. But they're not without questions.
2. Cubs
They were never a sure thing. They had too many young players still figuring things out. They also had some veteran starting pitchers who've thrown a lot of innings the past few seasons. The Cubs are still the NL Central's best team, and they will still probably be solid favorites to win a second straight pennant. But this first month has exposed some potential long-term issues, and it has possibly tightened the division race.

3. Dodgers
They survived a ridiculously large number of injuries last season to win the NL West. That's not the kind of thing a team could do two years in a row. Yet the Dodgers' disabled list is already peppered with big names: Rich Hill, Joc Pederson, John Forsythe and Andre Ethier. But the Dodgers have the deepest team in the game and arguably their best farm system ever. If they don't win a fifth straight division championship, it would be a major upset.

Four second-tier teams
Now to the second level of favorites, that is, the teams that have been to the postseason in recent years and would surprise almost no one by going again. Here are four.
1. Cardinals
St. Louis' rotation was best in the Majors in April with a 3.32 ERA, and that was supposed to be the biggest issue. Unfortunately, the Cards' offense produced only 99 runs, 22nd overall in MLB. And the defense -- the thing that was the focus of the offseason -- is still shaky. St. Louis' biggest hope is that the defense will get better as the weather warms up, and Matt Carpenter, Stephen Piscotty and William Fowler will start to produce, and this team will be back in the postseason for the sixth time in seven seasons.

2. Giants
San Francisco began the season with two irreplaceable players: Madison Bumgarner and Buster Posey. Now Bumgarner is sidelined indefinitely with a shoulder injury, and the offensive hole in left field has not been filled. On the positive side, Player Page for Matt Cain is again pitching at a high level, and once Matt Moore and Jeff Samardzija begin rolling out the quality starts, the Giants should be back in contention at some point. There's still too much talent and too much of a winning history to think anything else will happen.

3. Pirates
The Bucs' rotation is young and talented, and good enough to keep them in the mix with just a little help from the bullpen and offense. Unfortunately, Pittsburgh's offense scored just 90 runs in April, fourth fewest in the Major Leagues. Outfielder Starling Marte's PED suspension reduces the margin for error, and increases the pressure on Andrew McCutchen, David Freese, etc., to perform at a high level. There's enough of a track record on all those guys to believe that they will.

4. Mets
They overcame a long injury list to make the playoffs last season, and now they will be forced to do so again. There's still talent. Yoenis Cespedes will return to the lineup. Zack Wheeler needs to step up and fill the rotation spot behind Jacob deGrom and Matt Harvey. It's not an ideal situation, but it wasn't ideal last season when the Mets made a second straight postseason appearance.

Five for fighting
Now to five teams that have already made things interesting, and have the potential to keep making things interesting. Funny thing is, they have a common thread: mix of veterans youngsters in the everyday lineup with a pitching staff chock full of big potential young arms.
1. Rockies
It's about the pitching. Kyle Freeland and Antonio Senzatela have been very good. Tyler Chatwood must pitch the way he pitched last season. And then, Colorado needs Jon Gray to come back from the disabled list and contribute, even if it's just for the second half of the season. With Greg Holland anchoring the ninth inning, the Rockies have a chance to pitch the way they have only occasionally in franchise history.

2. Diamondbacks
The D-backs are similar to the Rockies with an experienced lineup and some young starters -- Patrick Corbin, Robbie Ray and Taijuan Walker -- lining up behind Zack Greinke. General manager Mike Hazen may have to acquire a piece or two for Arizona's bullpen, but former top prospect Archie Bradley has emerged as a potential stopper.

3. Brewers
Eric Thames has been the sweetest surprise story of the 2017 season, and is part of an offense that could slug Milwaukee right back to October. If Jimmy Nelson and Wily Peralta get hot and deepen the rotation, the Brewers could be the most surprising team in the Majors.

4. Marlins
Miami's bullpen is good enough. The offense probably is good enough. Now about that rotation, which was supposed to be a strength. It still may be. The best news for the Marlins is that the NL Wild Card race will involve enough teams knocking one another off that they'll have time to get straightened out.

5. Phillies
Philadelphia came out of April a game under .500 (11-12) thanks to a middle-of-the-pack offense and a competitive starting rotation (3.98 ERA). In a division in which the teams behind the Nationals appear to be fairly even, the Phils' young core could make things interesting.