Estes gave up a single to Aaron Boone and then walked Dmitri Young. He uncorked a wild pitch, putting runners on second and third. Estes then hit Lastings Milledge with a pitch to load the bases.
After getting ahead of Jesus Flores 1-2, Estes gave up a grand slam, and all of a sudden it was 4-0 Nationals.
"I made a really bad pitch [to Flores]," said Estes. "Obviously the guys getting on base was the biggest concern. The walk and the hit-by-pitch, I just didn't execute. And then, obviously, I made a bad pitch trying to get a double play, and left a fastball up in a spot where he could barrel it. He did what he was supposed to do. He hit a mistake, and unfortunately it came at a really bad time."
Estes said the pitch was supposed to be down and away, but he left it up.
"Unfortunately he hit it out of the park," said Estes. "A lot of time you might get a line drive there and score just one run. I got it elevated, and he got it out. But I'm more concerned that we lost the game because of it, so that's disheartening."
Estes couldn't really pinpoint the problem, and neither could his manager.
"From my viewpoint, the fastball command left him, the feel of the breaking ball left him," said Padres skipper Bud Black. "For whatever reason, he came out of his mechanics and just couldn't locate the ball. He got ahead of Flores, tried to throw a sinker down and away and left it up over the outer part of the plate, and that guy has some power."
The Padres battled back in the late innings, as they had done in winning their last two games.
Trailing, 6-1, San Diego struck for three runs in the bottom of the seventh. Back-to-back doubles by Luke Carlin and Tony Clark produced one run, and Scott Hairston's two-run home run off reliever Brian Sanches made it 6-4.
"It was a pitch out over the plate. I knew it had a chance," said Hairston of his seventh homer of the season. "I was hoping it would go out, and it did."
Luis Ayala, the third Washington pitcher of the inning, got out of the frame without anymore damage. Ayala pitched a scoreless eighth before Jon Rauch came on in the ninth and earned his 11th save in 13 opportunities.
Perez wound up pitching 6 1/3 innings, allowing three runs on six hits. He walked three and struck out four.
Estes pitched five innings, giving up four runs, walking two and striking out three.
The Padres got a run back in the fifth on an RBI single by Tad Iguchi before the Nationals took their 6-1 lead with single runs in the sixth and seventh off reliever Mike Adams. Milledge hit his third homer of the season in the sixth.
"We did battle back and had the tying run at the plate a couple of times," said Black. "We had our opportunities, but just couldn't get the big hit. We got down 4-0 and 6-1, and we fought back to where they had to bring in their closer, but we couldn't get that hit."