The NL East-leading Mets (57-44) lost 8-4 to lowly Pittsburgh on Thursday, ending a three-game winning streak. It was just New York’s second loss in seven games as it played for the second straight day without Beltran, who strained an abdominal muscle during batting practice Wednesday.
The All-Star center fielder, who tops the Mets with 19 homers and is tied with David Wright for the team lead with 62 RBIs, remains day to day.
“We’re waiting to see if it calms down,” manager Willie Randolph told the Mets’ official Web site. “It wasn’t like he took a swing and collapsed.”
Randolph also said Beltran could be a candidate for the disabled list if he doesn’t show improvement.
“There’s always a chance,” Randolph said.
Beltran was batting .381 (8-for-21) with three homers and six RBIs during a five-game hitting streak before the injury, but the Mets could be fine if he’s out for a longer amount of time.
Lastings Milledge, who’s moved over to center with Beltran out, continued his solid play on Thursday with his second homer in three games. Milledge is 10-for-20 with six RBIs in his last five games.
Jose Reyes went 2-for-4 with a homer for the Mets on Thursday, but the last-place Pirates scored five runs in the sixth inning and three in the seventh to avoid the series sweep.
“Everything happened kind of quick,” Randolph said.
Jorge Sosa (7-5, 4.36 ERA) will try a third time for his first win since coming off the DL on July 16.
Sosa, who was out with a strained left hamstring, allowed six runs and eight hits in four innings of an 8-6 road loss to the Los Angeles Dodgers on Saturday. He last won at Philadelphia on June 30.
The right-hander is 1-4 with a 6.90 ERA in six starts since opening the season 6-1 with a 2.64 ERA. He is 2-1 with a 4.15 ERA in six games - four starts - against the Nationals.
Catcher Jesus Flores went 2-for-4 with a go-ahead three-run homer in the eighth inning of Washington’s 7-6 victory at Philadelphia on Thursday.
The last-place Nationals are 14 games behind the Mets in the division.
Young, who snapped an 0-for-11 skid Thursday, is on the verge of signing a two-year, $10 million extension with the Nationals. Released by Detroit late last season, Young leads Washington with a .333 batting average and 53 RBIs.
Mike Bacsik (3-6, 4.39 ERA) looks to win his second straight decision for the Nationals on Friday. The left-hander allowed three hits in 6 2-3 scoreless innings for his best outing of 2007 in a 3-0 win over Colorado on Saturday.
“It was a fun day,” said Bacsik, who will make his first appearance against the Mets since going 4-4 with a 5.77 ERA in 16 games - 12 starts - for them from 2002-03.
New York is 3-2 against the Nationals this season and the clubs split the two previous games at Shea Stadium.