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5/28/2014 8:28 P.M. ET

Roster additions instrumental in Astros' success

KANSAS CITY -- Two waiver claims and a guy who joined the team less than a month ago.

Those were three of the biggest contributors to the Astros' 3-0 win over the Royals on Tuesday.

Collin McHugh, claimed off waivers, pitched seven brilliant innings for Houston before giving way to Tony Sipp, added to the roster on May 2, who sat down four in a row and extended his scoreless-innings streak to 9 2/3 this season.

Alex Presley, another waiver claim, collected three hits for the second straight game and added a sacrifice fly.

"Those are huge pickups when you look at the impact that they've had on our ballclub," manager Bo Porter said after the game.

Their performances were not simply one-game mirages, but more a reflection of how Houston has concocted its four-game win streak and nine wins in its last 14 games.

McHugh spent two forgettable seasons with the Mets and Rockies, when he accumulated an 0-7 record in nine starts and an 8.69 ERA in 2012-13.

Nevertheless, the Astros saw something in him and were rewarded. In seven starts this season, he has a 2.80 ERA and a 0.978 WHIP.

McHugh flummoxed the Royals with his 12-to-6 curveball. Kansas City struck out seven times on the curve, and McHugh has allowed only one hit in 48 at-bats (25 strikeouts) against the pitch, according to brooksbaseball.net.

"When you've been around a little bit and seen a couple different organizations ... you kind of have a bit of a chip on your shoulder, you want to prove some people wrong," McHugh said after the game.

Sipp has been nearly unhittable thus far. Of the 31 batters he's faced this season, only one has a hit off him. He's walked just one batter, and it was intentionally.

Presley entered the three-game series with the Royals batting just .218, but his six hits helped his team claim the first two games, and his batting average now sits at a respectable .250.

Astros maximizing starting pitching talent

KANSAS CITY -- Houston currently has an enviable problem: too much pitching.

With six starters vying for five spots, manager Bo Porter announced that his team will temporarily employ a six-man rotation.

Porter set his rotation for Houston's four-game home series with the Orioles. Brad Peacock goes Thursday, with Brett Oberholtzer following him Friday. Dallas Keuchel (Saturday) and Scott Feldman (Sunday) will fill the weekend slots.

Keuchel, Feldman, Collin McHugh and Jarred Cosart are locks for the rotation, with the upcoming starts from Peacock and Oberholtzer presumably serving as auditions for the final spot.

"Good pitching is always a good problem to have," Porter said. "I'll take eight of them, we'll find somewhere for them to pitch."

Rookie sensation George Springer deserves a lion's share of the credit for the Astros' recent surge, but without solid starting pitching of late, Houston's 10-5 record in its last 15 games would not be possible.

In the last 23 games since May 5, the rotation's ERA sits at 3.18.

"Our starting pitching has been tremendous," Porter said. "I think it's contagious; the next guy up feels like they want to out-do the guy who threw the night before or the day before."

Houston blackout lifted for Civil Rights Game

Major League Baseball plans to lift the blackout for Friday's Civil Rights Game for all fans in the Astros' viewing territory. The game will be available on MLB Network.

The game between the Astros and Orioles will air nationally with Harold Reynolds, Matt Vasgersian and Sam Ryan calling the action. Both teams will wear Negro Leagues throwback uniforms. The Astros will don the colors of the Houston Eagles (1949-50), and the Orioles will be wearing the uniforms of the Baltimore Elite Giants (1938-50).

The first 15,000 fans to enter Minute Maid Park on Friday will receive a special commemorative Civil Rights Game cap, and the Astros will treat fans to a postgame fireworks show with a Motown theme.

The Civil Rights Game began in Memphis, Tenn., in 2007, centering on an exhibition game between the Cardinals and Indians. After another exhibition game in Memphis in '08 between the Mets and White Sox, the Civil Rights Game moved to Cincinnati ('09-10), then Atlanta ('11-12) as regular-season contests, and last year was hosted in Chicago by the White Sox.

Astros all right against southpaw starter

KANSAS CITY -- With lefty-killer Danny Duffy on the mound for the Royals, Astros manager Bo Porter opted for an entirely right-handed lineup Wednesday.

That means Chris Carter, Carlos Corporan and Jesus Guzman all earned starts for the first time in the Kansas City series.

Left-handed batters were hitting 1-for-23 against Duffy this season with a .197 on-base-plus-slugging percentage.

"This guy, he's been tough on lefties," Porter said. "We're going to run that right-handed lineup at him and see if we can score some runs."

Carter, who sat out the last three games, served as the designated hitter, while Corporan and Guzman slotted into catcher and first base, respectively.

George Springer immediately got the Astros on the board in the first inning of their 9-3 victory with a two-run home run off Duffy, his ninth of the season and sixth in as many games. Carter clubbed a solo home run in the fifth inning, then added a three-run shot off right-hander Louis Coleman in the sixth. Corporan had an RBI double in the third.

The Astros chased Duffy in the fifth, touching the lefty for six runs (five earned) on seven hits and drawing five walks.

Triple-A stint works wonders for Fields

KANSAS CITY -- Josh Fields hit rock bottom on May 6.

The Astros reliever allowed six hits and five runs in just two-thirds of an inning against the Tigers.

The outing was far from an outlier either.

From April 23 to his implosion versus Detroit, Fields allowed a whopping 14 earned runs in just three innings.

A ticket to Triple-A Oklahoma City followed.

"I looked at it as more a time to refocus and kind of get back in that mindset that I needed to be in," Fields said. "I thought it was a great opportunity, and I was excited to learn and try to get better."

Thus far, Fields has returned a changed man.

With another shutout inning on Monday against the Royals, Fields extended his scoreless streak to six innings since being recalled on May 17.

During that stretch, Fields allowed just one hit and notched 10 strikeouts.

"I think I was pressing a little too much before that, trying to do a little too much, getting out of what I do to be successful," Fields said. "I just tried to relax and have fun when I went down there, and when I came back up here I just tried to carry that over."

Worth noting

• Astros pitcher Jose Cisnero underwent successful Tommy John surgery on his right elbow Wednesday morning. Cisnero appeared in five games this season before being placed on the disabled list on May 7. His ERA was 9.64. The 25-year-old made 28 relief appearances last season for the Astros, posting a 4.12 ERA in 43 2/3 innings.

Brian McTaggart is a reporter for MLB.com and writes an MLBlog, Tag's Lines. Follow @brianmctaggart on Twitter. Jackson Alexander is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.