Reason for optimism: There isn't another team in baseball that wouldn't trade its roster (contracts included) for the Cubs'.
Reason for pessimism: It's nearly impossible for Jake Arrieta to provide as much value in 2016 as he did in 2015, but it doesn't matter.
In 33 starts last year, Arrieta allowed a total of 52 runs -- the same amount the Phillies' Justin De Fratus allowed ... out of the bullpen. But that figure is actually deceivingly high because of the way they were distributed. In terms of win expectancy, the best way to allow your runs over the course of a season is to bunch them all in one game. Arrieta didn't do that, of course, but he did allow a total of zero or one run (earned and unearned) in 15 of his last 20 starts (and 20 out of 33 overall). Zack Greinke may have edged Arrieta for the ERA crown, but not even he had a 20-game stretch of starts that gave his team such an overwhelming chance to win.