It took a moment for J.A. Happ to feel comfortable in a Pittsburgh Pirates uniform. The way he's pitching now, he may never want to take it off.

Happ will look to extend his personal streak and help his new club to a seventh win in eight games Saturday night against the visiting Colorado Rockies.

After going 4-6 with a 4.68 ERA in 20 starts with Seattle, Happ was acquired by the wild card-leading Pirates at the trade deadline. The left-hander's first start was rocky, a 5-0 loss to the Chicago Cubs on Aug. 4 in which he lasted 4 1-3 innings and gave up nine hits and four runs.

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Happ (2-1, 2.08 ERA) appears to have figured it out, though, allowing one run over 17 1-3 innings in his last three starts, tossing six scoreless in wins over Arizona and Miami in his past two outings. It's the first time the 31-year-old has logged back-to-back starts of at least six innings without allowing an earned run since September 2010.

"I'm just kind of getting back to me being aggressive in the strike zone and trying to get ahead of hitters," Happ told MLB's official website. "We tried to work on a few things, minor mechanics-wise, then mentally to just trying to keep that aggression, keep that focus and that confidence in every pitch and throw with conviction.

"For whatever reason, pitchers sometimes get away from that, I know I did, but it's nice to get back in the right frame of mind and feel good about being out there."

He's contributed to a Pittsburgh (78-49) team that has won six of seven and 13 of 16 after Friday's 5-3 victory over Colorado. Gregory Polanco had three hits for the Pirates, who are 20-4 against the NL West.

The Rockies (51-75) lost for the 13th time in 17 games and their sixth straight at PNC Park despite Carlos Gonzalez's fifth home run in 10 contests.

They'll try to avoid another defeat when they send the inconsistent Chris Rusin to the mound.

Rusin (4-6, 4.97 ERA) threw his first career shutout in a 5-0 win over San Diego on Aug. 16 but followed it with his shortest start since September 2012 last Saturday.

During a 14-9 loss to the New York Mets, the left-hander lasted just two-plus innings and surrendered career highs of 11 runs and 12 hits - including a team-record eight doubles.

He became the second pitcher in the last 70 years to give up 11 runs after completing a shutout.

''It's one of a starter's worst nightmares," Rusin said. "You don't ever wish it upon anybody, you don't wish it upon yourself. It's one of those things you have to forget about, wipe away, have a short term memory and get started on the next team you're about to face.''

Rusin is 1-2 with a 4.19 ERA in four career starts against the Pirates.

Andrew McCutchen, Aramis Ramirez and Jordy Mercer have each homered off Rusin in limited at-bats, and Pedro Alvarez is 4 for 8 against him.

Happ is 1-0 with a 1.93 ERA in three career starts against the Rockies, though he hasn't faced them since 2011.