On Tuesday, J.A. Happ (4-11) allowed seven hits and five runs, but Houston's offense bailed out the left-hander in a 7-6 win. Happ, who had been 0-7 over his previous 10 starts, posted his first triumph since May 14 against the New York Mets.
Michael Bourn went 3-for-5 with three RBI, and his two-run double capped a four-run fourth inning. Clint Barmes smacked a two-run homer and also drove in three runs for the Astros, winners in just two of their last nine games.
Michael Morse and Jerry Hairston Jr. each had three hits and hit two-run homers for the Nationals, who took the opener, 5-2, on Monday behind Ryan Zimmerman's go-ahead RBI single in the ninth inning.
Myers, meanwhile, is winless in five straight starts - losing four - since a complete-game defeat of the Los Angeles Dodgers on June 17. In that game, at Dodger Stadium, Myers allowed an earned run on four hits with a walk and six strikeouts while improving to 3-6 on the season.
He's allowed two, three, five, six and three runs since while pitching at least six innings four times. The Astros are 1-4 in those starts and 6-14 in his 20 overall outings.
Myers is 10-9 with four saves in his career against Washington.
Right-hander Livan Hernandez also takes aim at his first win of July for the Nationals.
Hernandez upped his record to 5-8 with a 2-1 defeat of the Chicago White Sox on June 26, but is winless in three subsequent starts while allowing 14 runs in 16 2/3 innings.
He was touched for three earned runs on eight hits in four innings while losing an 11-1 verdict at Atlanta in his last start July 15.
Hernandez is 10-6 with a 4.35 earned run average in 17 career starts against Houston.
The Nationals and Astros split eight meetings last year, but Houston did win three of four at home.