Cubs also signed Koji Uehara to a one year deal yesterday.
And for cheap, too.
Fangraphs currently has the Cubs tied with the Yankees for best bullpen in their WAR projections. That's subject, of course, to Jansen's signing. If he goes back to the Dodgers, I'd expect them to vault up to #1.
Still, if everyone is relatively healthy - far from guaranteed with Davis, Uehara, and Rondon - the Cubs could have a top 3 in the majors bullpen. And I still expect them to sign a left hander. Boone Logan would be my choice.