I'm not too worried about the Cubs bullpen as long as the starting rotation holds up and Maddon doesn't overwork them like he has in recent years. On paper if the rotation is healthy and productive as they can be getting 6-7 innings consistently from the starters will go a long ways towards keeping the pen fresh and sharp. Last year with Darvish being hurt, Chatwood sucking, and even Lester and Q having problems getting 5+ innings in at times really put a lot of usage on the bullpen and the guys you need fresh and sharp down the stretch were probably overworked and tired out from all the innings they had to eat up from short starts. Monty started a career high 19 games so that took the 1 guy that usually could eat up multiple innings out of the pen out of the mix too.
Maddon's use of the bullpen has been questionable for years too. Sometimes pulls starters too soon or lets someone like Edwards pitch to a few too many batters on days when it's obvious he doesn't have good command of his pitches. It's been mentioned before that he nearly cost the Cubs the World Series with how he used Chapman too.