Arrieta goes for 20th win in key NL Central matchup with Pirates

Arrieta, Cubs try to gain ground on Pirates (1:11)

Mark Mulder previews the Wednesday Night Baseball matchup between the Cubs and Pirates. (1:11)

Jake Arrieta, already in historic company with his recent stretch of great performances, goes for his 20th win of the season when the Chicago Cubs visit the Pittsburgh Pirates on Wednesday Night Baseball (7 p.m. ET, ESPN/WatchESPN).

Here are some of the key storylines for tonight's game:

Arrieta making history

Arrieta has won his last eight starts, allowing a total of three earned runs over 58 1/3 innings in the process. That's good for an 0.46 ERA.

The Elias Sports Bureau notes that only one other pitcher has won eight consecutive starts with an ERA under 0.50 in a single season since earned runs became official in 1913: Bob Gibson had an 0.25 ERA while throwing eight consecutive complete games in 1968.

Arrieta is looking to become the first Cubs pitcher to win 20 games in a season since Jon Lieber in 2001. He has already racked up 204 strikeouts; only two Cubs pitchers since 1900 have won 20 games in a season while striking out 200 or more batters. Ferguson Jenkins did so five seasons in a row, from 1967 to 1971, and Orval Overall did it back in 1909.

With a win on Wednesday, Arrieta would become the first 20-game winner of the season. The Elias Sports Bureau also notes that only two Cubs pitchers in the live-ball era (since 1920) have been the first pitcher in baseball to reach 20 wins in a season: Larry Jackson in 1964 and Charlie Root in 1927. Rick Sutcliffe was the first to 20 in 1984, but he did not start the season with the Cubs.

Arrieta has an ERA of 1.99 entering Wednesday's game. The last Cubs starter that finished the season with a sub-2 ERA and qualified for the ERA title was Grover Cleveland Alexander in 1920.

Despite that, Arrieta trails Zack Greinke (1.61 ERA) for the league lead. Entering this season, 13 qualified starters in the last 40 years have finished a season with an ERA below 2.00. Five of those pitchers didn't win the Cy Young award that season.

Pirates pitching

Though Arrieta is arguably having the best individual season on either team, the Pirates pitching staff has had an impressive season. Pirates pitchers have a 3.18 ERA this season, trailing only their division rival St. Louis Cardinals (2.85 ERA).

The Pirates rank third in ERA by starting pitching this season at 3.46. A.J. Burnett (3.14 ERA), who recently returned from injury, starts for the Pirates on Wednesday.

Burnett, 13 strikeouts away from 2,500 in his career, has been a much better pitcher at PNC Park this season. Despite his home record (2-3), he has a 2.33 ERA and 1.20 WHIP at home this season, compared with a 4.03 ERA and 1.46 WHIP on the road.

Despite missing over a month with an injury, Burnett is third in the NL this season with 68 curveball strikeouts, trailing only Clayton Kershaw (87) and Madison Bumgarner (72). The Cubs have the fifth-most strikeouts against curveballs this season.

The Pirates are also second in ERA by relief pitchers this season at 2.70. Closer Mark Melancon has contributed to the success of the Pirates' pen this season, posting a 2.00 ERA while tying the team's single-season saves record with 46.

Melancon has had success against the Cubs in his career, posting a 1.76 ERA in 40 career games against them, but has struggled against them in 2015.

Melancon has allowed four earned runs in eight innings against the Cubs this season, as many has he had allowed in 33 innings against them entering this year, though three came in one game in April.