The 2004 Chicago Cubs didn't make the postseason despite having an excellent rotation of starting pitchers. 

Chicago had Kerry Wood, Greg Maddux, Matt Clement, Mark Prior and Carlos Zambrano. Zambrano led the way with a 2.75 ERA, followed by Clement (3.68), Wood (3.72), Prior (4.02) and Maddux (4.02). 

It's a shame this team didn't make it to October with the talent they had on the mound.