Wrigley Field playing as extreme pitchers’ park this season

Strange as it might seem, the Cubs and White Sox will be playing in one of the best pitchers’ parks in baseball Tuesday and Wednesday.

Wrigley Field, long regarded as a hitters’ haven, is one of three parks in the National League and one of six in the majors with runs park factors below .820, as listed at ESPN.com. The Cubs are at .810, meaning they and their opponents have combined to score only 81 percent as many runs per game at Wrigley as in Cubs road games.

The toughest park on hitters has been Petco Park in San Diego at .710, followed by Target Field in Minneapolis (.760), Yankee Stadium (.773), Oakland Coliseum (.801), Chase Field in Phoenix (.808) and Wrigley.

On the South Side, Guaranteed Rate Field has been the sixth-best hitters’ park at 1.162. The nightmare park for pitchers, as is often the case, has been Coors Field in Denver at 1.575.

It long has been known that Wrigley is a different environment when the wind is blowing in than when friendly breezes carry the ball out of the park.

There are compensating factors. The greenery in center field give hitters a good background, and the foul territory is small. That means hitters get extra chances on pop-ups that would be foul outs in other parks.

In the past, that has left Wrigley as a strong hitters’ park when the wind is blowing out, better than average for hitters in weak or neutral winds and below average for hitters with winds blowing in. On balance, it has favored hitters overall.

Not so in 2019. Wrigley’s park factors this season favor pitchers, with .659 for home runs, .899 for hits, .950 for doubles and even .969 for walks.

That’s not business as usual at Wrigley. Last season, park factors included 1.079 for runs and 1.025 for homers (anything above 1 is better than average for hitters). In 2017, factors were 1.131 for runs and 1.005 for homers.

The last time Wrigley played as a pitchers’ park was in the Cubs’ World Series season of 2016, with an .874 factor for runs and an .819 factor for homers.

You can see the difference in pitching and hitting splits. Cubs hitters have scored 170 runs and hit 46 homers in 35 home games; they have scored 193 runs and hit 67 homers in 36 road games. Cubs pitchers have allowed 123 runs and 29 homers at Wrigley and 179 runs and 50 homers on the road.

That doesn’t mean there has been a fundamental change in Wrigley’s nature. Chance factors, including wind and weather, play a role. It’s for that reason that Baseball-Reference.com uses three-year averages in park-adjusted metrics such as WAR. It also excludes interleague games to eliminate differences in using designated hitters.

But for the nearly half-season we’ve seen in 2019, Wrigley has been one of the extreme parks. And the surprise is that the favored extreme is on the pitching side.