By Bruce Levine —

CHICAGO (CBS) — The Cubs decided that a promotion of an unlikely rookie pitcher in the middle of a heated pennant race was worth a gamble Thursday night.

With right-hander Jake Arrieta still on the disabled list and left-hander Mike Montgomery showing signs of fatigue and needed in the bullpen, Cubs management chose 22-year-old right-hander Jen-Ho Tseng, their minor league pitcher of the year, to start a crucial game amid a tight playoff race.

The gamble turned out fine for the Cubs — only because a near-historic offensive explosion continued in a 14-6 win against the Mets at Wrigley Field. Trailing 3-0 and 5-3 early, the Cubs later reeled off 11 unanswered runs, giving them a total of 39 in the three-game sweep and their most in a three-game series since 1987.

Tseng had a poor outing, showing signs of nerves from the beginning. He walked a batter, made an error and hit one in the first inning. His went three innings, allowing five runs, all earned, on five hits and a walk while striking out six.

“I was really a little nervous before the first pitch,” Tseng said through a translator. “After that, I was more comfortable. I threw a 3-2 cutter behind a batter and became more nervous.”

The decision to start Tseng was based on trying to buy time for the return of Arrieta, who’s been the Cubs’ best starter for most of the season and is recovering from a hamstring strain. The smart money has Arrieta returning late next week if there are no setbacks along the way.

The Cubs backed Tseng by battering Mets right-hander Seth Lugo, who allowed eight runs, seven earned, in three innings. The Cubs scored five times in the fourth inning to take control with a 9-5 lead. Anthony Rizzo and Jason Heyward homered in the game.

Manager Joe Maddon, who could find a positive in a natural disaster, praised Tseng’s work, statistics be darned. Tseng worked with Taylor Davis, his catcher at Triple-A Iowa.

“I like the kid a lot,” Maddon said. “They as a battery had that ‘never let them see you sweat’ moment. We did. Jen-Ho showed me great carry on his fastball. I loved his changeup. That was his first time out. There is something is in there. An awkward first night for him. Moving forward, I really like him.”

The Cubs now hold a three-game lead in the NL Central over the Cardinals and Brewers. St. Louis visits Chicago for a three-game series that starts Friday afternoon.

“It was important not to overlook this series against the Mets,” Rizzo said. “We know we have a big series with the Cardinals this weekend. It was important to play them here one at a time. Our offense hit the ball well.”

Bruce Levine covers the Cubs and White Sox for 670 The Score and Follow him on Twitter @MLBBruceLevine.

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