Next Up: The Chicago Cubs

The Pirates have won six in a row, after having dropped four in a row (including three to the Cubs). Here's how the National League Central standings looked on the morning of September 19, before the Pirates embarked on their hot streak, taking two in Los Angeles from the Dodgers and four in Denver from the Rockies:

      St. Louis   92  55  ---
      Pittsburgh  87  60  5.0
      Chicago     86  61  6.0

And here's what a six-game winning streak buys you:

      St. Louis   97  56  ---
      Pittsburgh  93  60  4.0
      Chicago     89  63  7.5

Best record in baseball over the past week, and all it yields is one game against the division leader and one and a half over your nearest rival. The top of this division is just ridiculous.

How Are They Doing Lately? Continuing on that theme, over the past 30 days, the Cubs have a 16-12 record, fifth best in the league, trailing the Cardinals (17-11) by a game and the Pirates (18-11) by a game and a half. That makes the Cubs a game short of joining the Cardinals and Pirates as playing .600-plus ball over the past 30 days. During that period, the Cubs have scored 4.8 runs per game, fourth in the league, while giving up 4.1 runs per game, the sixth fewest. The Pirates are one slot ahead of the Cubs in both categories, scoring 4.9 and giving up 4.0 per game. 

What's Going Right? Not a lot has changed since the teams met in Pittsburgh a week and a half ago. Cubs starting pitchers have the second best ERA in the league, 3.49, over the past 30 days, with the third highest strikeout rate, third lowest walk rate, fourth lowest rate of hard contact allowed, third highest rate of inducing swings outside the strike zone, and lowest rate of home runs allowed on fly balls. The bullpen's been less spectacular but still good: 3.49 ERA, sixth in the league, with the fourth highest strikeout rate and second highest rate of ground balls induced. At the plate, the Cubs are fair at getting on base (their .253 batting average over the last 30 days is tenth in the league and their .329 on base percentage is seventh) but they've got power. Their .428 slugging percentage is third in the league, powered by the most doubles and third most homers in the league over the past 30 days. That gives them a .175 isolated slugging average (slugging percentage minus batting average, measuring pure power), second only to the Mets.

What's Going Wrong? Two pitching measures that tend to regress toward the mean are batting average on balls in play and percentage of baserunners left stranded. A team that's unusually good has probably been a little lucky, and a team that's unusually bad has probably been a little unlucky. The Cubs bullpen has the third-lowest batting average on balls in play and the fourth-highest strand rate in the league over the past 30 days, which suggests they haven't been as good as they've seemed. The Cubs hitters present a particular challenge for the Pirates pitching staff because the Cubs generate a lot of fly balls--their ratio of ground balls to fly balls is the third lowest in the league over the past 30 days--while the Pirates pitchers, as you probably know, rely on grounders, with the second highest ground ball/fly ball ratio in the league over the same period. Just as with lefty/righty platoons, fly ball hitters tend to do well against ground ball pitchers, and vice-versa. So the fly ball-happy Cubs batters could pose problems for the grounder-focused Pirates hurlers. On the other hand, the Pirates, somewhat contrary to their pitch-to-contact reputation, generate a fair number of strikeouts, with the fifth-highest K rate in the league over the past 30 days, and the Cubs are free swingers, with the second-highest strikeout rate and highest rate of whiffs on swings (26%) over the past 30 days. If the Pirates pitchers succeed, it may be less by generating ground balls and more by generating strike three against the whiff-prone Cubs.

Who's Hot? Jake Arrieta is the Pirates' main impediment to advancing in the postseason. He's the logical candidate to start a wild card play-in game against the Pirates, and he seems unstoppable. Over the past 30 days, the majors' first 20 game winner has a 0.43 ERA. He's allowed a .182 batting average on balls in play and he's stranded 93% of the runners who've gotten on base, which indicates a little luck, but you need good luck hitting against him: 42 strikeouts, 24 hits plus walks over his last 42 innings. He starts Sunday night's ESPN game. Kris Bryant, solidifying his Rookie of the Year credentials, has a .330 batting average, .377 on base percentage, and .585 slugging percentage over the past 30 days, though he's struck out in nearly a third of his plate appearances. His 23 RBI over the period tie him for third in the league. Starlin Castro, who has emerged as the team's top second baseman, has put up even better numbers, .386/.413/.643, albeit in more limited play. Corner outfielder Chris Coghlan (aka the guy whose takeout slide seriously injured the Pirates' Rookie of the Year contender and best second-half player, Jung Ho Kang) has a .375 on base percentage over the past 30 days, and first baseman Anthony Rizzo's is .361. 

Who's Not? Tomorrow afternoon's starter, Jason Hammel, may be pitching himself into the Cubs' bullpen during the postseason; he has a 6.20 ERA over the past 30 days and hasn't allowed fewer than three runs in a start in over a month. Rookie shortstop Addison Russell flashes impressive leather but is hitting just .181 with a .258 on base percentage over the past 30 days, and rookie left fielder Kyle Schwarber has a .176 batting average and .291 on base percentage over the same period. Schwarber's whiffed in nearly a third of his plate appearances, Russell almost 37% of his. 

What's the Outlook? The last Cubs series was a disaster for the Pirates, losing three straight after winning the first game, culminated by the season-ending (and, very possibly, 2016 season-delaying) injury to Kang. And those games were in Pittsburgh. Now they travel to Chicago after playing yesterday afternoon in the Mountain time zone (the Cubs had the day off) for two afternoon games followed by a Sunday night game. The latter game means they'll be wrapping up their Sunday six hours later than the Cardinals, who'll be at PNC for three do-or-die games starting Monday. So there are all sorts of ways for the Pirates' internal clocks to get messed up, relative to those of the Cubs and Cardinals. Plus, we'll find out, as some have posited, whether four games in the altitude of Coors Field screws up hitters' swings and timing. (One guy whose swing probably won't be affected: Andrew McCutchen has hardly had a chance to swing, having walked 13 times in his last 21 plate appearances.) Taking two of three in Chicago--a necessity if the Pirates are going to have a shot at catching the Cardinals and getting reasonable distance between themselves and the Cubs in the battle for home field advantage in the wild card game--strikes me as a tall order.