By Bruce Levine–

CHICAGO (CBS) — Baseball has had its share of September marvels who pushed their way into a playoff picture and beyond. In 1978, the Dodgers brought up right-hander Bob Welch late in the summer, and he helped them win the pennant before his classic matchup with the Yankees’ Reggie Jackson became legendary. In 1980, Philadelphia Phillies right-hander Bob Walk was promoted during the season and helped pitch the organization to its first World Series title in decades.

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On Thursday, the Cubs will turn to a little-known name themselves as the NL Central race hangs in the balance. They’ve promoted 22-year-old right-hander Jen-Ho Tseng from Triple-A Iowa and will start him against the New York Mets in the series finale at Wrigley Field. In a corresponding shift, the Cubs are sending left-hander Mike Montgomery back to the bullpen as right-hander Jake Arrieta continues to recover from a hamstring injury. Tseng’s spot in the rotation could last one game or more, and giving the Mets a different look was part of the equation in the Cubs’ thinking.

Tseng was 13-4 with a 2.54 ERA in 145 1/3 innings in 24 starts across Double-A Tennessee and Triple-A Iowa this season, and he was named the Cubs’ minor league pitchers of the year Wednesday. His performance included a 6-1 mark with a 1.80 ERA in nine starts at Triple-A.

Though it may feel like one, this isn’t a last-minute decision by the Cubs. After Tseng’s season ended the first week of September, the Cubs sent him to Arizona to pitch in a simulated game for five innings and stay sharp.

Late Thursday afternoon, Cubs president of baseball operations Theo Epstein and others swung by manager Joe Maddon’s office to offer Tseng as a temporary stopgap for the rotation. Maddon saw the logic in the move as it returns Montgomery (3.64 ERA) to the bullpen.

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“We needed more help in the bullpen”,” Maddon said. “So Montgomery is so versatile and amenable. We talked about it, and he is available in the pen. Jen-Ho was in town to accept an award (Friday for being the team’s minor league pitcher of the year). I said to him, ‘I know you are in town to accept an award, but how about starting tomorrow’s game instead?’ He didn’t even blanch. I have heard nothing but good things about this kid. I have watched him on video. We think right now, in order to get us all set up pitching-wise, this is the right thing to do.”

If Tseng pitches well, he may get a second start. The plan buys Arrieta time between now and a week from today to get back from his hamstring strain. Arrieta will likely throw two side sessions or a simulated game before coming back.

“It could be one and done,” Maddon said of the Tseng experiment. “We will see how it all plays out. He is a really good command pitcher. He throws and probably hits high 80s to low 90s. He is kind of like (Kyle) Hendricks with a really good changeup. He has a nice breaking ball also. He knows what he is doing out there. Sometimes you catch lightning in a bottle and learn things too.”

The Cubs will start John Lackey on Friday as they open a three-game series against the Cardinals, and he’ll be followed by Kyle Hendricks on Saturday and Jose Quintana on Sunday.

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