They're in a tough spot in regards to pitching. Lester - Hendricks - Quintana is a very good top 3, the problem is once you start filling in that rotation with the rest of the in house names, the depth is non-existent. And you when you start to realize that Lester's best years are behind him it starts looking very thin very fast. Filling out the bullpen likely requires a mid level $5mil/ acquisition as well.
Signing someone like Darvish gets them right back in the driver seat in the central, but the odds of that aren't very high. I'm assuming they'll sign somebody more on the Alex Cobb / Lance Lynn tier of FA pitchers, but that still requires a good chunk of money.
Outfield is an up gradable spot as well, but thats tough to do via FA. Zobrist and Heyward are eating a lot of $$ for not a lot of production. They'll likely run Schwarber out there in left again, but i doubt they'll be able to afford giving him another ~500 below average plate attempts.
The Cardinals are an infield upgrade and innings eater starter away from being within striking distance of the Cubs on paper as it stands now.