Dave Martinez is in danger of missing the playoffs in his first season as an MLB manager. (Rob Carr/Getty Images)
Sports Columnist

The Nationals have reached the must-win part of their schedule. After a stretch that included 20 losses in 29 games, they can either quickly reverse an awful slump by the All-Star break or face the fact that their season is already trashed with the second half left to play.

Entering Thursday’s game against Miami, the Nats were 42-43, about 10 wins fewer than expected. They’re in third place in the NL East, a division they were expected to win for the third straight time. A popular World Series pick by national pundits, Washington is simply an inconsistent, OK team.

Don’t say it’s too early to judge the Nationals. The season has surpassed its midpoint. Not many teams dramatically improve after the first half.

Don’t say injuries are to blame. The Nationals have been healthy enough to win more than they have, and they’ve gotten a surprise addition with 19-year-old Juan Soto emerging from the minors to be their best bat. Don’t say poor pitching is at fault, because Max Scherzer has taken four losses in his past five starts. Washington got shut out in three of those games.

Maybe you can point a finger at poor managing. Dave Martinez is having a pretty lousy rookie season. Entering Thursday, the Nationals were 8-16 in one-run games. Martinez has often left pitchers in too long and has overseen a team with sloppy baserunning that has killed rallies.

The skipper has shuffled the lineup more than a Las Vegas poker dealer. Now cries to bring back Dusty Baker, who managed the Nats to 95 and 97 wins in two seasons, don’t seem over-reactionary.

Eleven games against three teams with losing records should show whether Washington can dig itself out of this rut. The Nationals host the Marlins for four — Thursday’s game ended after Express’ deadline — then visit Pittsburgh for three days and close the first half with four games at the Mets. If the Nats can’t manage at least 7-4 against the trio entering the All-Star break, then the already slim chances of seeing October baseball in Washington get worse.

After the break, the Nats return with series against the NL East-leading Braves and the NL Central-leading Brewers. Failing to steal either of those series could leave Washington wondering if the Nats are buyers or sellers at the July 31 trade deadline.

The Nationals look lost, much like they did in 2013 and 2015, when division titles were followed up with mediocre efforts that led to turnover at manager.

When the Nats are working in Bryce Harper at first base for an emergency — or maybe to get someone batting better than .215 into the outfield — that’s a red flag. When Harper is watching a potential homer hit the wall and manages only a double after jogging to first, as he did this week against Boston, that’s a red flag. Aside from his homers (21 entering Thursday), he’s having a rough season. He’s the engine of this team but has shown few signs of reversing his worst start.

The Nats have a small window to figure out whether they’re actually contenders. It will be a grind to the finish to make the playoffs.

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