Nationals catcher Matt Wieters is thrown out trying to steal in the eighth inning Sunday against the Rockies. (Brad Mills/USA Today Sports)

The Washington Nationals are struggling, and they are six games out of first place in the National League East. The New York Mets are winning, and they’re six games up on the Nationals. A mid-April series has rarely felt so pivotal to these Nationals, who have not had to scratch and claw so soon since 2015. No series played in the spring will define a season, nor even make or break it. Even if the Nationals were to take two of three from the Mets this week, they would still find themselves under .500. But a series win would certainly help, particularly after a gut-wrenching 6-5 loss to the Colorado Rockies ended a 3-7 homestand Sunday afternoon. They doomed themselves repeatedly during that stretch, fighting through defensive miscues and self-sabotage on the bases as they lost several close games.

In fairness to the Nationals, the are not the only projected division winner to not look the part yet. The Dodgers are in last place in the National League West. The Cubs are 7-7, battling weather, injuries and inconsistency. Nothing is decided, and the Mets will not play this well forever. But slowing them down would certainly stabilize the situation before the Nationals head to California for a two-city swing.

Meet the Mets

The Mets struggled this weekend, which for that team, at this time, means they actually lost a game. But they will head into Monday’s series opener at Citi Field on a high note after noted Nationals nemesis Wilmer Flores hit a walk-off homer against old friend Matt Albers on Sunday afternoon. They are 12-2, in the midst of a charmed start that qualifies as the best in franchise history. Their starting rotation is healthy, which has always been the differentiating factor for this team. Their veteran lineup boasts experience, particularly against this Nationals staff, and has also stayed healthy. Veterans like Asdrubal Cabrera and Todd Frazier are off to hot starts.

The Nationals will catch a break in that they will miss stifling Noah Syndergaard. They will also get a chance to see former backup catcher Jose Lobaton, who is in the big leagues because of injuries to both of the Mets’ Opening Day catchers. Their .731 team OPS is only two points higher than the Nationals’, and they have scored two fewer runs. They have not exactly been dominant offensively, either. But as the Mets swept the Nationals in Washington last week, they looked more in control, tighter defensively and smarter offensively. Their record reflects the early difference.

Injury risks

As in 2015, when injures piled up and left the Nationals scraping for runs with a makeshift lineup, nicks and bruises are diminishing their run-scoring ability again early. The team got good news this weekend: Daniel Murphy will head to West Palm Beach to start playing in extended spring training games. His return is not far off.

But other than Murphy’s return, the Nationals seem to lose more firepower by the day. Adam Eaton is still on the disabled list with a bone bruise in his ankle, though all indications are that he will not be out much longer than the 10 days required for such a stint. He is eligible to come off the DL the day after the series with the Mets ends.

Their primary fill-in for Eaton, Brian Goodwin, has been battling a sore wrist since Wednesday, but he pinch-hit Sunday and seems likely to be able to play this week. Anthony Rendon, meanwhile, has missed two games with a “sore” big toe after fouling a pitch off it Friday night.

The Hellickson era begins

Though A.J. Cole bounced back with 5 1/3 strong innings against the Braves last week, the Nationals will give veteran Jeremy Hellickson a chance to earn the fifth spot in their rotation — a chance that will begin with a matchup against Jacob DeGrom and the Mets on Monday night. That Hellickson would get a chance was a foregone conclusion. That it would come in such a relatively important April matchup was not. He has been pitching against minor league players in extended spring training, which is a long way from Citi Field.

Hellickson is no stranger to the NL East, and many Mets have long histories against him. Cabrera, for example, owns a .391 batting average against the righty in 25 plate appearances. Yoenis Cespedes has three homers in 19 at-bats. The key will be changing speeds, creating a substantial difference between his low-90s/high-80s fastball and his change-up. He has built himself up to 90-plus pitches in extended spring, and he should be ready to shoulder a typical starter’s workload Monday night.

Probable pitchers

Monday: RHP Jeremy Hellickson vs. RHP Jacob DeGrom

Tuesday: LHP Gio Gonzalez vs. RHP Zack Wheeler

Wednesday: RHP Tanner Roark vs. LHP Steven Matz

More Nationals coverage:

Daniel Murphy to play in extended spring training games starting this week

Nationals finish frustrating homestand with another tough loss to Rockies

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