PITTSBURGH -- Keeping his emotions under control has helped Jake Arrieta become arguably the best pitcher in the major leagues. So it wasn't surprising that he took setting a Chicago Cubs' franchise record in stride.

Arrieta pitched seven scoreless innings to extend his regular-season winning streak to 17 games -- breaking the record set by Rick Sutcliffe in 1984 -- as the Cubs beat the Pittsburgh Pirates 7-1 on Tuesday night.

"At this point, it's business," Arrieta said. "It's cool to think about those kind of things. We all know the career that Rick had, just gives me a little ammo against him, but for now we've got to turn the page quickly."

Arrieta (6-0) allowed just two hits while striking out five and walking two to improve to 17-0 with a 0.55 ERA in 18 starts since last Aug. 1. He has also won nine straight starts, the longest streak by a Cubs pitcher since Milt Pappas won 11 in a row in 1972.

The walks came to the first two batters in the bottom of the first inning but Arrieta escaped the jam and was never threatened again. His coolness is what struck Pirates outfielder Matt Joyce who went 7-for-14 in the American League when Arrieta struggled with the Baltimore Orioles before being traded to the Cubs in 2013.

"He probably has similar stuff, but what I could tell facing him now is that he didn't make any mistakes," Joyce said. "He doesn't get out of his zone. Walking the first two hitters in a game didn't faze him one bit. He wasn't upset with himself. He wasn't frustrated. It's pretty amazing stuff."

Arrieta also became the first Cubs in more than a century to win his first six starts in a season. Hall of Famer Moredcai "Three Finger" Brown did so in 1908.

"His work ethic is impeccable," Cubs manager Joe Maddon said. "You saw it tonight. He struggled early then once he finds out where the ball is going, everything takes off for him. He's going to keep going down this path with his skill and the way he works."

The Cubs' Kris Bryant extended his hitting streak to nine games by going 3-for-5. Anthony Rizzo hit two doubles for the second night in a row and scored the game's final run in the ninth inning on Ben Zobrist's sacrifice fly while Tim Federowicz also had two of Chicago's 11 hits.

The Cubs improved their major league-best record to 19-6 with their sixth win in seven games and are the first team not to lose back-to-back within the first 25 games of a season since the 2003 New York Yankees.

Chicago is as many as 13 games over .500 in the first 25 games or fewer since the 1969 team did so in 24 games. The Cubs have also won 21 of their last 24 road games.

Jon Niese (3-1) was ripped for six runs and nine hits in five innings after winning his first three decisions in a season for the first time in his nine-year career. The left-hander walked five and struck out three.

"He wasn't able to get the ball where he needed to get the ball," Pirates manager Clint Hurdle said.

Sean Rodriguez had two of Pittsburgh's three hits and John Jaso drove in the lone run with his eighth-inning ground out. It was the third loss in a row for second-place Pirates (15-12) and dropped them five games behind the Cubs in National League Central standings.

Arrieta has pitched 23 consecutive scoreless innings against the Pirates, including a five-hit shutout in last year's NL wild-card game, and improved his career record against them to 8-1.

Zobrist hit an RBI double and scored on Arrieta's single as the Cubs took a 2-0 lead in the second inning.

The Cubs added four runs in the fourth as Addison Russell scored on a wild pitch and Jorge Soler and Kris Bryant delivered consecutive RBI singles before Rizzo capped the inning by doubling home a run.

NOTES: Cubs OF Matt Szczur (strained right hamstring) was placed on the 15-day disabled list and OF Ryan Kalish had his contract selected from Triple-A Iowa. ... Cubs RF Jason Heyward (sore right wrist) sat out a second straight game. ... Pirates LF Starling Marte did not start for the first time this season as he was rested. ... Cubs LHP Jon Lester (2-1, 1.83 ERA) will start Wednesday afternoon against Pirates RHP Juan Nicasio (3-2, 3.33) as Chicago tries to sweep the three-game series.