The Mets took two of three from Washington last weekend at Shea Stadium to improve to 10-9, but went on to lose two of three to Atlanta.
The Nationals, meanwhile, lost two of three to Philadelphia after last weekend’s series in New York.
On Wednesday, Mets starter Tom Glavine gave up seven runs, 12 hits and three walks in 4 1-3 innings as New York fell 8-4 to Atlanta for its second straight loss.
Cliff Floyd pulled the Mets to within one run with his sixth homer of the year, a two-run shot in the fourth inning, but that was as close as New York would get.
Floyd got a hit in his 14th straight game, tying Rey Ordonez for the longest April hit streak in franchise history. He is batting .358 (19-for-53) with five homers and 15 RBIs during the streak.
“I have one approach and I stay with it. See the ball and give myself a chance,” Floyd said. “When things are going well, it seems real simple.”
The Mets, who started the season 0-5, were last under .500 on April 20 at 7-8.
Washington lost for the fifth time in seven games Wednesday, 3-0 to Philadelphia.
“A lot of my outings, just one bad pitch cost me the game,” Loaiza said, “and it cost me the game today.”
Loaiza allowed four hits and faced just three batters over the minimum before the ninth inning.
“Loaiza pitched an outstanding game, and we came away with a loss,” Nationals manager Frank Robinson said. “We cannot afford to lose games like that.”
Washington hasn’t been under .500 since it was 3-4 on April 11.