In his past four starts, Millwood gave up three runs twice and two runs twice to fall behind early. On Sunday, David Wright started trouble early by hitting a two-run homer to give the Mets a 2-0 lead three batters into the game.
Chris Carter added a three-run homer later in the inning for the 5-0 advantage. Millwood now has allowed 15 runs in the first inning of his past five starts, falling to 0-8.
"I thought early in that first inning, I don't think his location was as good," said Orioles interim manager Juan Samuel. "Then, he kind of settled down and started feeling better as the game [went on]. But at that point, the damage was done."
Millwood gave up a total of eight runs on 11 hits in 5 1/3 innings and is still looking to find the consistency that's eluded him throughout the season. He's now given up 31 hits in his past three starts, and he leads the Major Leagues with 19 home runs allowed.
The veteran right-hander said afterward that he's probably been trying too many things to get everything right. He'll be working on clearing his head a bit before his next start.
"I'm just not throwing the ball where I need to," Millwood said. "That's pretty much it. And hopefully I can figure something out between now and the next time and get back to where I was before."
The Orioles (17-46) actually found some offense early against one of the game's best pitchers, getting three runs on five hits against Mike Pelfrey (9-1) in the first two innings. But the big right-hander also settled down and made it through six innings, allowing just the three runs.
Baltimore put Pelfrey in constant in trouble in the first two innings. The Orioles got two on with none out in the first inning and scored two runs thanks to a Luke Scott sacrifice fly and an single from Adam Jones, who had three hits on the day and added another RBI single in the seventh.
They also got the first two runners on in the second and scored on a Miguel Tejada RBI single to make it 5-3.
Pelfrey settled down after that, however, and the Orioles got only one run on six hits in the final seven innings. The Mets scored the next six runs to blow the game open.
"I didn't have a feel for anything," Pelfrey said. "Everything was up, everything was flat. I felt like they were racing for the bat rack. Luckily, today was a good day to put up some runs. I'll definitely take it."
The Mets (35-28) got the power that the Orioles haven't been able to find all season. Wright hit a pair of homers, going 3-for-5 with four RBIs.
Jason Bay belted a solo shot and snapped an 0-for-16 slide by going 4-for-4. A triple in the ninth would have given him the cycle, but Bay reached on an infield single as part of the Mets' 18-hit attack in which every starter got at least one hit.
New York finished with four homers on the day and seven for the series. Baltimore didn't hit any, a big reason it was swept in a series for the eighth time this season.
The Orioles -- once again -- struggled with runners in scoring position, going 2-for-8. Baltimore finished the series with a .171 average with runners in scoring position (6-for-35) and have a .217 average in that situation this season.
Baltimore left 10 on base, wasting a number of opportunities.
"When we get runners in scoring position, [we must] be aggressive -- don't let a good one go by," Jones said. "We're going up there trying to, it's just not working right now for us."