Michael Taylor will try to build on an impressive major league debut and help the NL East-leading Nationals match a team record by continuing their road dominance of the New York Mets on Wednesday night.
Werth has been sidelined by an aching right shoulder since Sunday.
"He is not reacting well. We'll try to treat him again, get him going again. He feels sore," manager Matt Williams told MLB's official website. "I don't think it's a DL-type situation. ... I don't think there isn't any major issue. I think it's inflamed and sore."
Williams may feel comfortable giving the right fielder an extended break after Taylor singled and hit a two-run homer in Tuesday's 7-1 win at New York (57-63).
"Definitely better than I imagined," said the 23-year-old Taylor, who hit a combined .315 with 22 homers, 63 RBIs and 35 stolen bases in the minors this year.
Washington's success in Queens, however, goes beyond Taylor, as the Nationals (64-53) are hitting .296 with 26 homers while averaging 7.4 runs during a nine-game winning streak there, the longest active by a visiting team at a specific venue.
It's also one shy of the franchise record, set by the Montreal Expos against the Chicago Cubs from 1982-83.
Washington is 23-4 in its last 27 games at Citi Field, hitting at least four homers in five of those games to come one short of the Mets' total since the park opened in 2009.
Desmond has homered on half of his eight hits in 23 at-bats over his last six overall meetings with the Mets, while Rendon is 9 for 23 with three homers and 10 RBIs in six road matchups.
Jordan Zimmermann (7-5, 3.06 ERA), who is 1-0 with a 2.21 ERA in his last three starts, is facing New York again after allowing three runs in 6 1-3 innings of a 5-3 win in 13 on Thursday.
The Mets counter with Bartolo Colon (11-9, 3.97), who is 3-1 with a 3.25 ERA in his past four starts.
The right-hander was terrific Friday, allowing one run in eight innings of a 5-4 win at Philadelphia, joining Pedro Martinez and Juan Marichal as the only Dominican-born pitchers to reach 200 career victories.
"He was pitching to contact," catcher Travis d'Arnaud said. "I mean, balls were getting hit, but they were getting hit off the end of the bat or getting jammed."
Colon, a member of the Expos in 2002, has a 3.21 ERA while splitting two meetings with Washington this year. He was charged with a 5-1 loss at home April 2, giving up three runs and two homers - one to Desmond - in six innings.
Desmond is 3 for 6 with two homers in their matchups, but Colon has held Harper and Rendon to a combined 1 for 10 with six strikeouts.
New York's David Wright has an 11-game hitting streak after going 2 for 4 Tuesday, while Nationals center fielder Denard Span's 14-game run came to an end after an 0-for-5 night.