Joe Maddon knows that if his Chicago Cubs want to be considered a serious postseason contender, they must prove themselves against the best teams in baseball. Chicago (39-32) already took the season series from NL East-leading Washington and prevailed over Clayton Kershaw and Zack Greinke while splitting a four-game home set with the first-place Los Angeles Dodgers this week. "Pretty good showdown this weekend," St. Louis pitcher Lance Lynn said.