PHILADELPHIA -- The Phillies thought they upgraded their rotation on Tuesday.

Instead, they found themselves scrambling. The Phils agreed to a trade in the afternoon for Pirates left-hander Tyler Anderson, only to see the deal fall apart because Pittsburgh had a medical concern about one of the two prospects Philadelphia agreed to send. Hours later, the Phillies watched their starting pitching fall short again in a 6-4 loss to the Nationals at Citizens Bank Park, reinforcing the need to find a replacement for Anderson before Friday's 4 p.m. ET Trade Deadline.

Left-hander Matt Moore allowed a three-run home run to Josh Bell in the first inning and a three-run homer to Juan Soto in the second inning to put Philadelphia in a 6-1 hole. The Phillies (50-50) never recovered, wasting an opportunity to move within 2 1/2 games of the Mets (53-46) in the National League East.

Moore has a 10.80 ERA (12 earned runs in 10 innings) in his last two starts, a 5.86 ERA (18 earned runs in 27 2/3 innings) in six starts since he returned from the injured list last month and a 6.98 ERA (30 earned runs in 38 2/3 innings) in nine starts overall.

He has pitched five or more innings just three times.

“Everybody understands the bargain here, right?” Moore said. “So there are ends that need to be held up. Just speaking personally, it doesn’t really change things for me, mostly because I try to really only focus on the things that are within my control. That’s scouting this team. That’s making sure all my ducks are in a row heading into this start.”

Anderson had been expected to replace Vince Velasquez in the rotation, not Moore, but on Tuesday night Anderson was headed to Seattle instead.

Maybe Velasquez will start on Thursday as scheduled. Or maybe the Phillies will find somebody before then.

“You can always use starters, of course,” Bryce Harper said. “Starting pitching wins games. Pitching and defense. I’ve always said my whole career: pitching and defense wins. Timely hitting, of course. But pitching and defense will always be king in this game. If you have the guys that you need to go out there and throw you five-, six-plus innings, it’s always going to be good for you. We need to be better.”

“We need to do better,” manager Joe Girardi echoed.

And that includes the defense. Didi Gregorius did not make a clean play on a ground ball from Trea Turner in the first inning. Turner reached safely and later scored on Bell’s homer. Gregorius missed a fly ball in foul territory during Robles’ leadoff at-bat in the second. (He later walked.) Moore retired the next two batters, so he should have been out of the inning. Instead, he allowed a second baserunner before Soto’s blast.

“That’s a play [Gregorius is] usually going to make and he didn’t,” Girardi said of the ball in foul territory. “It’s a long run. You start to get near the fence. But it’s a play he’s capable of making.”

Gregorius is struggling both offensively and defensively. He is batting .213 with a .652 OPS, but Girardi did not shoot down the idea that he might play infielder Ronald Torreyes more frequently at shortstop.

“I try to work through it every day, where people are at and how they’re doing,” Girardi said. “I’ll continue to consider everything every day. We’re at that time of year.”

The Phillies can do little things like that to improve the defense. But what they really need is pitching, and they don’t have much internally. The Phils know they cannot overcome big deficits like this every night.

“It’s very tough as an offense to come out each night and try to score six, seven, eight runs,” Harper said. “It’s just not possible, especially with the pitching in this division and in this league as well. Tough night for us, but I thought we battled the best we could. We never really gave up.”