By Bruce Levine–

CHICAGO (CBS) — Starting pitching continues to be the engine that keeps the Cubs on the track to an NL Central title and a playoff berth.

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On Wednesday, right-hander Jason Hammel engineered seven shutout innings, winning his 12th game of the season as the Cubs were 3-1 victors against the Angels at Wrigley Field. Scattering four hits while walking two and striking out six, Hammel lowered his ERA to 2.90 as the Cubs ran their winning streak to a season-best nine games and reached 30 games over .500 for the first time since last September.

The win came with a downside, as setup man Pedro Strop injured his left knee while fielding a ball that was topped down the third-base line by Yunel Escobar in the eighth inning. As Strop picked up the ball while third baseman Javier Baez and catcher Willson Contreras also converged, he awkwardly bent his left leg under his right. Strop came up lame and never made a throw.

He had to be helped off the field after trying a couple knee bends.

“He hurt his knee,” manager Joe Maddon said. “That is all I know right now. He will get his (MRI) test tomorrow morning, and I will know more. It was really an unfortunate moment. He will be tested tomorrow morning, and we will know more at that point.”

Strop was the second Cubs setup man to be lost in the past three days. Right-hander Hector Rondon was shelved for the last three games with a right triceps strain remains day-to-day. Before the game, Maddon said Rondon was making strides to return to the bullpen. The Cubs will probably bring two pitchers up from Triple-A as a precaution if they’re to lose Strop for any length of time.

Chicago’s starting staff has the lowest ERA in baseball at 2.91. On Wednesday, Hammel struggled with pitch count early but settled in after the fourth inning.

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Hammel is 5-0 with a 1.16 ERA since the All-Star break.

“With Jason, if he knows where his fastball is going, he can pitch deep into games,” Maddon said. “He has good movement and good off-speed pitches. I think he has a tough angle for a lot of hitters because he is so tall. It is not complicated — on any given night, if he or any of our pitchers are commanding their fastball, they can pitch deep into a game.”

The Cubs defense once again came up big. Web gems by Baez and shortstop Addison Russell have become almost routine lately, and that was again the case. Russell charged a slow chopper in the eighth with the potential tying run storming home and made a tough play look easy by one-handing it and throwing it to first for the out.

In the bottom of the inning, Russell hit his 13th homer, matching his total from his 2015 rookie season.

“I like the do or die play,” Russell said of his big defensive play. “With all of my teammates watching me make that play, it makes it pretty sweet.”

The Cubs are 8-0 in August, their best start in this month since matching that mark in 1927.

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Bruce Levine covers the Cubs and White Sox for 670 The Score and CBSChicago.com. Follow him on Twitter @MLBBruceLevine.