NEW YORK -- On a cold, windy Sunday, the D-backs completed their three-game series with the Mets by falling 5-0 at Citi Field.

With the loss, the D-backs fell to 3-6 on the season, with a four-game series in Washington against the Nationals starting Monday night.

Here are some things to know about what transpired for Arizona on Sunday:

Their hitting struggles continued
The bats have been quiet for the D-backs for much of the season, and Sunday was no different, as they were 1-for-9 with runners in scoring position.

It was the second time they've been shut out this season, and despite leading off the fourth and sixth with doubles, they were unable to take advantage.

"We got people in scoring position," D-backs manager Torey Lovullo said. "We had the potential to build big innings, and we just didn't get the job done. Hitting with men in scoring position is a very tough chore. It's not a wrestling match when you're up there at home plate. You've got to just relax and walk up to home plate with a clear mind and follow the process, and then stay with your plan instead of trying to do too much. And I think that's what we're doing right now [trying to do too much]."

Fundamental mistakes continue to hurt
Sloppy defense and fundamentals were a big problem for the D-backs last year. They spent a lot of time this spring trying to correct that.

They've been better at some points this year, but at other times their problems have come back. Sunday was one of those times.

"There's a couple plays that I think [if] we make and we execute and do things differently, it's a totally different game, and we’ve got to tighten that type of stuff up," Lovullo said. "So yeah, was it frustrating? Absolutely. But these things were all things we talk about, practice and they're identifiable and we've got to improve on them."

With the game scoreless in the sixth and Pete Alonso at first, Eduardo Escobar blooped a ball to right. Pavin Smith raced in, picked the ball up and fired to second to try to nab Escobar, who was trying to stretch his hit into a double.

The throw sailed high and wide, allowing Alonso to score and Escobar to reach third.

"I had a grip on [the ball] and thought I could get him at second and I overthrew," Smith said. "I just tried to throw it as hard as I could, and it definitely sailed on me."

The D-backs are going to be flexible with the fifth starter spot
It was a surprise when the D-backs announced at the end of Spring Training that Luke Weaver, who was expected to be the fifth starter, would instead pitch out of the bullpen.

Caleb Smith got the nod instead on the basis of an outstanding Spring Training, but after allowing five runs (four earned) in one-plus inning in his first start, the D-backs shifted him to the bullpen and put Humberto Castellanos in the rotation in his place.

Smith allowed five runs in relief against the Mets on Friday and was optioned to Triple-A Reno prior to Sunday's game.

While in Reno, Smith will pitch out of the bullpen in a long role. If he comes back to the D-backs, his role will likely be as a multi-inning reliever.

Castellanos, meanwhile, battled tough conditions -- 48 degrees with a 24 mph wind at gametime -- to throw four shutout innings.

That likely gets Castellanos another start, but as the D-backs have shown early this year, performance and matchups will determine what happens with that fifth spot in the rotation.