Nationals open four-game series against Diamondbacks (May 10, 2018)

PHOENIX -- Perennial MVP candidates Bryce Harper and Paul Goldschmidt will meet once again in a four-game series at Chase Field this weekend beginning on Thursday.

This time, with a twist.

Harper is the Washington Nationals' new leadoff hitter.

Goldschmidt is off the slowest start of his stellar career with the Arizona Diamondbacks.

Tired of watching opponents pitch around Harper in the third spot, manager Dave Martinez moved Harper to leadoff on May 1, two days after the Diamondbacks took two of three in a series at Nationals Park.

Harper has hit the last four of his NL-leading 12 homers from the top of the lineup, although he has been in a little bit of a funk recently, going 0-for-19 after homering in his first two plate appearances against Philadelphia last Friday. He received his first day off of the season in the Nationals' 2-1 loss at San Diego on Wednesday.

"For me it's not only about 162 (games), it's about 163-64-65 and so forth," Martinez told reporters Wednesday. "You have to keep that in mind. And we do. I've been to the playoffs a lot as a coach now. Rest matters, it really does."

Goldschmidt has uncharacteristically struggled recently, too. He snapped an 0-for-26 streak with a single in a 12-inning road victory against the Los Angeles Dodgers on Tuesday, and he has not homered since April 15, a career-long stretch of 88 plate appearances.

He had an RBI single in a 6-3 loss to the Dodgers on Wednesday, his first RBI since April 21, and his strikeout rate has been higher than normal. After averaging a strikeout about every 4 1/2 plate appearances the last four seasons, he has fanned about 30 percent of the time this year.

"I think now it is pitch selection," Arizona manager Torey Lovullo said before the start of the quick two-game series at Dodger Stadium.

"You are only as good as the pitches you swing at. I know it's a cliche, but it makes so much sense. Getting that foot down and paying attention to the zone, surveying the zone, balls and strikes. For some reason, he is not swinging at good pitches right now. He knows that. I know that he is working on it. We know that he is going to come around. You take the law of averages. You take the track record."

Arizona's Zack Greinke (3-2, 4.10 ERA) will oppose Washington right-hander Tanner Roark (2-3, 3.65) on Thursday as the Diamondbacks look to extend their strong start.

The Diamondbacks (24-12) have played 12 series and are 10-0-2 in them, splitting a four-gamer and a two-gamer with the Dodgers. They have won eight of 12 against the Dodgers this season and are through with them until Aug. 30 after this series.

Washington (20-18) has won nine of its last 11 games.

The Nationals' surge began with a 3-1 victory over the Diamondbacks in the final game of a three-game series at Nationals Park on April 29. Arizona left-hander Robbie Ray was forced out of that game with an oblique injury after getting one out in the second inning. He is expected to miss at least six weeks.

Right-hander Kris Medlen made the start when Ray's turn came around again last Friday, and he was optioned to the minors the next day. Because of an off day Monday, Arizona can turn to Greinke on regular rest.

A.J. Pollock, who has 11 homers, homered among his three hits and had two RBIs in a 5-4 victory over Washington on April 27 in the first game of that recent series. He also walked with the bases loaded to force in the winning run in the 10th inning of the second game.

Harper walked four times in that series, twice intentionally, which seemed to be the final straw in the decision to move Harper to the leadoff spot. Harper had six hits in his first three games there, including homers in the first two.

Greinke missed the series at Washington earlier this season and has not faced them since joining the Diamondbacks in 2016. He is 5-1 with a 1.49 ERA in seven starts against the Nationals, his most recent start against them coming as a member of the Dodgers in 2015. He pitched 14 scoreless innings in two victories against the Nationals in 2015, giving up nine hits and striking out 17.

Greinke is 2-0 with a 1.85 ERA in four home starts, extending the Chase Field success he found in 2017, when he was 13-1 with a 2.87 ERA in 18 starts. He was 5-5 with a 4.81 ERA in 13 starts at home in his first year with the Diamondbacks, 2016.

Roark did not face the Diamondbacks earlier this season either, and is 2-2 with a 3.02 ERA in nine career appearances, including six starts, against them.

Roark was 1-1 with a 4.15 ERA in two starts against Arizona last season, when he gave up only nine hits and struck out 19 in 13 innings. Two of those hits were homers. He won his start at Chase Field, giving up three hits while striking out 11 in seven innings.