Facing a Detroit Tigers team he's had plenty of success against lately could help Washington stay hot.
The Nationals seek a sixth victory in seven tries in the conclusion of a two-game interleague set with the Tigers on Thursday.
Washington (18-15), coming off having the NL's best record and an NL East title in 2012, dealt with its share of struggles early and carried a sub-.500 record into May.
The Nationals seem to have gotten on track, though, after winning four of five to end a recent road trip before beating Detroit 3-1 on Wednesday. Bryce Harper entered this short series 4 for 29 (.115) over his previous eight games, but his solo homer and sacrifice fly helped back another stellar performance from Jordan Zimmermann.
''We didn't get much off a hot pitcher even though I thought we had pretty good at-bats off him, to be honest with you.'' Tiger manager Jim Leyland said.
Detroit's problems may continue against Haren, who has been solid over his last two starts after posting a 7.36 ERA through his first four.
Haren (3-3, 5.01 ERA) gave up two runs in six innings of a 6-3 win over Cincinnati on April 27 before allowing one run and four hits in eight frames of a 3-1 win at Atlanta last Thursday.
"I was trying to do too much (early in the season)," Haren told the team's official website. "I just backed off and pitched like myself (the last time out). I didn't pile up too many strikeouts, but I didn't have many two-strike counts."
Haren's teammates know he has plenty more solid performances in him, too.
"His last two starts have been good; that's what he's capable of doing," said outfielder Denard Span, who tripled Wednesday. "That's the three-time all-star Dan Haren right there."
The right-hander has pitched extremely well versus Detroit in recent years, going 3-0 with a 1.76 ERA in four starts since 2008 including a shutout and another complete game.
The Tigers (19-12) hope to have better luck against him this time around after falling for only the second time in 11 games Wednesday. Miguel Cabrera, just 3 for 16 lifetime off Haren, drove in their only run with a single in the third after they scored 37 runs in a four-game sweep at Houston in their previous series.
Detroit will look to bounce back Thursday as it sends Doug Fister to the mound.
Fister (4-0, 2.48) wasn't at his best Friday, giving up three runs - two earned - and a season-high nine hits while striking out four in six innings in the Tigers' 4-3 win over Houston.
It marked the first time since his first start April 5 that Fister failed to pitch at least seven full innings and strike out at least five. The right-hander, though, has a 2.13 ERA over his last 12 starts - including the postseason - completing at least six innings in 11 of them.
''He was good. Maybe not quite as sharp as he's been, but still good,'' Leyland said. ''He kept us in the game and saved our bullpen.''
Fister has made one start versus Washington, allowing one run and three hits in eight innings of a 6-5 victory June 21, 2011, while with Seattle.