Updated May 29, 2011 7:18 PM ET

HOUSTON (AP)

The surprising Arizona Diamondbacks are in first place in the NL West. Shhhh. Kirk Gibson wants to keep it quiet.

Xavier Nady hit a two-run double in the eighth inning, helping the Diamondbacks rally for a 4-2 victory and a series sweep of the Houston Astros on Sunday.

Still, no bragging, please.

”We just need to remain humble and we’ll go to work this home stand,” Gibson said. ”We’ve got something planned for Tuesday, we got something planned for Wednesday. We’ll just keep seeking out and searching out to be better and better and to be able to handle more situations that are ahead of us.”

The Diamondbacks completed a 6-1 road trip and they are 14-2 in their past 16 games.

”It’s not a superstition, it’s just the way it is,” Gibson said. ”There are no guarantees. Nothing will ever be easy in this game.”

Nady’s go-ahead double off Jeff Fulchino (1-3) gave the Diamondbacks their first lead and Juan Miranda followed with an RBI single for a two-run cushion.

It was a comforting moment for Nady, since he struck out with the bases loaded in the first inning and took a called third strike in the fifth. Gibson gave Nady a boost after his first inning strikeout.

”He came up to me after I struck out with the bases loaded,” Nady said. ”You want to get a hit in a big situation like that and as the game went on I thought my swing was better and I was seeing the ball better. He kept me mentally fired up. He said you’re going to go get them.”

Gibson wasn’t in the dugout for Nady’s big hit. He was ejected in the fourth inning for disputing home plate umpire D.J. Reyburn’s balk call on pitcher Josh Collmenter.

”They said I stepped toward home,” Collmenter said. ”I took another look at my mark on the mound and it didn’t look like it but from his vantage point it might have looked different. I was surprised at that.”

So was Gibson, who came out to discuss the issue and was immediately tossed.

”I don’t want to get into that,” Gibson said.

Arizona’s rally spoiled a solid outing by Houston starter J.A. Happ, who hit his first major league home run. Happ allowed two hits over six innings.

Aaron Heilman (4-0) struck out the side in the seventh for the victory.

J.J. Putz pitched the ninth for his 16th straight save to start the season. It is the longest current streak in the major leagues.

Happ walked the bases loaded with one out in the first inning but didn’t allow a hit until Willie Bloomquist lined a single into center field with two outs in the fifth.

After loading the bases in the first, Happ retired the next 12 batters before Bloomquist’s hit.

”I settled in after that first inning,” Happ said. ”I threw more strikes, and I felt better as the game went on. I got a pitch to hit and luckily I put a good swing on it and caught it.”

Happ hit a solo homer on the first pitch from Collmenter in the fifth inning, the first of his career, giving Houston a 2-0 lead.

Happ walked four and struck out eight.

Collmenter pitched six innings, allowed four hits, walked one and struck out five. Collmenter didn’t allow a hit until Jeff Keppinger led off the fourth with a double into the left field corner. He went to third on a single by Hunter Pence.

With Brett Wallace at the plate, Reyburn called a balk on Collmenter, sending Keppinger home with the first run and Pence to second base.

Wallace walked but Chris Johnson grounded out and Clint Barmes struck out to hold Houston’s lead to 1-0.

Justin Upton tripled to the center field wall to lead off the sixth inning and scored on Chris Young’s sacrifice fly.

Pence extended his hitting streak to 10 games. Keppinger has hit safely in the two games he’s played this season since returning from the disabled list on Friday. Keppinger was 2 for 5 on Friday.

Gibson likes the way his team is playing.

”But we’ve got a long way to go and we talked about playing good baseball and it’s hard to sustain it,” he said. ”Our character will continue to be tested.”

NOTES: Collmenter has the Arizona franchise record with 15 consecutive scoreless innings to begin his career as a starter. Kelly Johnson has a five-game hitting streak, including a 4-for-5 performance Saturday night. Miranda has hit safely in eight of his last nine games. He hit two two-run homers in Friday night’s 7-6 Arizona victory.

HOUSTON (AP)—Xavier Nady(notes) hit a two-run double in the eighth inning,
helping the Arizona Diamondbacks rally for a 4-2 victory and a series sweep of
the Houston Astros on Sunday.

Arizona has won six straight road games and 14 of 16 overall. Nady’s
go-ahead double off Jeff Fulchino(notes) (1-3) gave the Diamondbacks their first lead
and Juan Miranda(notes) followed with an RBI single for a two-run cushion.

Arizona’s rally spoiled a solid outing by Houston starter J.A. Happ(notes), who hit
his first major league home run. Happ allowed two hits over six innings.

Arizona manager Kirk Gibson was ejected in the fourth inning after disputing
a balk call.

Aaron Heilman(notes) (4-0) struck out the side in the seventh for the victory.

J.J. Putz(notes) pitched the ninth for his 16th straight save to start the season.
It is the longest current streak in the major leagues.

Happ walked the bases loaded with one out in the first inning but didn’t
allow a hit until Willie Bloomquist(notes) lined a single into center field with two
outs in the fifth.

After loading the bases in the first, Happ retired the next 12 batters
before Bloomquist’s hit.

Happ hit a solo homer on the first pitch from Josh Collmenter(notes) in the fifth
inning, the first of his career, giving Houston a 2-0 lead.

Happ walked four and struck out eight.

Collmenter pitched six innings, allowed four hits, walked one and struck out
five. Collmenter didn’t allow a hit until Jeff Keppinger(notes) led off the fourth with
a double into the left field corner. He went to third on a single by Hunter
Pence(notes).

With Brett Wallace(notes) at the plate, umpire D.J. Reyburn called a balk on
Collmenter, sending Keppinger home with the first run and Pence to second base.

Gibson came out to dispute the call and was immediately ejected.

Wallace walked but Chris Johnson(notes) grounded out and Clint Barmes(notes) struck out to
hold Houston’s lead to 1-0.

Justin Upton(notes) tripled to the center field wall to lead off the sixth inning
and scored on Chris Young’s sacrifice fly.

Pence extended his hitting streak to 10 games. Keppinger has hit safely in
the two games he’s played this season since returning from the disabled list on
Friday. Keppinger was 2 for 5 on Friday.

NOTES: Collmenter has the Arizona franchise record with 15 consecutive
scoreless innings to begin his career as a starter. Kelly Johnson(notes) has a
five-game hitting streak, including a 4-for-5 performance Saturday night.
Miranda has hit safely in eight of his last nine games. He hit two two-run
homers in Friday night’s 7-6 Arizona victory.