Dont' look at anything as a trap. Anything can happen at baseball at anytime Vegas doesn't need to set any traps. Anyway if they were setting a trap they would have the line at -130 or so. -180 scares everyone away and makes the payout less.
The fatigue factor is a little overhyped, think about it they get back to Chicago in time to sleep for 12 hours before they have to get to the ballpark and probably glad to be home. Jet Lag may be somewhat of a concern but these players are used to traveling as this has all they have know since they entered pro ball.
Now break down the game, J.D Drew's bat is at slider speed right now having trouble laying off high fastball and way behing it. Pujols doesn't have near the patience at the plate they he showed last year. Cardinals are putting Tino at cleanup who is still not used to the pitchers in the NL Central. The two hitters in the Cardinal lineup that should worry you in this game are Vina and Edmonds.
Take into acount that Lieber hasn't lost in Wrigley in 14 decisons or so and that he has 10 career wins vs. the Cardinals most vs. any team. Also take into account the the Cardinals pitching rotation is so banged up outside of Morris and Kile it is a AAA staff.
This is where you get your line of -180, not a trap