CHICAGO -- Manager Clint Hurdle often repeats one of the Pirates' principal hitting philosophies, something taught throughout the Minor League level and encouraged in the Majors. It sounds simple, but it's proven to be easier said than done. Hit the ball hard where it's pitched.
Bell's blast came first. With one out in the fourth, the rookie first baseman ripped a high and outside pitch from Arrieta just over the left-field fence at Wrigley Field for the Pirates' first hit.
"Bell took advantage of a pitch early," second baseman Josh Harrison said. "Pretty impressive."
But hardly a surprise for the rookie slugger, batting .407/.541/.704 in the Majors. Both of his homers -- Monday's and his dramatic pinch-hit grand slam on July 9 -- have come against the Cubs, and he has yet to record an out in four plate appearances against Arrieta.
Bell put the Pirates on the board, and Polanco pushed them ahead in the sixth, ripping a nearly identical high fastball to left for a three-run homer that gave Pittsburgh a 4-3 lead.
Polanco leads Pittsburgh with 21 home runs, more than he hit in his first two seasons combined, and 79 RBIs. Four of those homers have come in his last seven games, but it's equally encouraging to see where Polanco is going deep, not just when.
The 24-year-old shortened up his long lefty swing over the offseason, and the changes have paid off. He has hit four true opposite-field homers to left in his career, all of them this season and two of them within the last week, as he knocked a solo shot down the left-field line against the Astros on Tuesday.
Polanco's homer was the club's 11,000th in 130 seasons playing in the National League. Two innings earlier, Bell hit No. 10,999.
It was also the Pirates' best-case scenario against Arrieta, who allowed a season-high-tying six runs in 6 1/3 innings. He has allowed 12 earned runs in his last two starts against Pittsburgh after giving up nine total in his first 10 starts since joining the Cubs in 2013.
During that time, Pittsburgh's hitters have spoken about finding a way on base, forcing him to pitch from the stretch and, of course, hitting the ball where it's pitched.
"We stayed consistent with our plan," Hurdle said. "We got some good results later."
Adam Berry has covered the Pirates for MLB.com since 2015. Follow him on Twitter at @adamdberry. This story was not subject to the approval of Major League Baseball or its clubs.