The win was Karstens' fifth consecutive, earning him the honor for the shortened week ending July 17.
"It's an honor, just for us as a team to be able to get recognition now," Karstens said, minutes after the announcement. "We had three All-Stars this year. To get Player of the Week, yeah, it means a lot to us, but I think my biggest goal is to get us farther than we're at now."
Karstens scattered five hits and two strikeouts over nine frames for his second career shutout, becoming the first Pittsburgh starter to win five straight decisions since Ian Snell accomplished the feat from May 20-June 10, 2006.
Karstens' 83 pitches were the fewest thrown in a nine-inning complete game in the Majors this year and the lowest total since the Royals' Luke Hochevar needed just 80 against the Reds on June 12, 2009.
In eight starts since the beginning of June, Karstens has gone 5-0 with a 1.26 ERA to help lead the Pirates into contention in the competitive NL Central.
"You try and stay as even-keeled as possible, because you know you're going to have good moments, you're going to have bad ones," Karstens said. "It's just trying to minimize those stretches. If you put too much pressure on yourself, the game's not fun. The one thing I really strive to do is play, have fun and see where it takes me. It has done me well so far."
It is Karstens' first career weekly honor and the first Player of the Week honor for a Pirates pitcher since 2001, when Todd Ritchie won the award.