The Cubs' rotation is a bit of a concern moving forward, and compounding matters is that they seem very likely to lose Jake Arrieta and John Lackey via free agency. That's what prompted the Cubs to ink Tyler Chatwood to a three-year contract not long ago. 

The Cubs, of course, are squarely in contending mode, and you can be certain they're not done. Speaking of which, here's this from CBS Chicago's Bruce Levine: 

... [T]he Cubs are continuing their strong push to sign free agent right-hander Alex Cobb, sources said. The rumors on a Cobb-Cubs marriage have been out there for several months, and with the Winter Meetings starting Monday, Chicago would like land Cobb as quickly as possible to avoid any traps and new suitors that may await in the next week. 

Levine's story has more, including which team might give the Cubs the most competition for Cobb's services. 

As for Cobb, he's very open to the idea of coming to the North Side of Chicago, where he'd be reunited with Joe Maddon and Jim Hickey from their Tampa Bay days. Cobb, 30, is coming off a 2017 season in which he pitched to a 3.66 ERA (113 ERA+) and 2.91 K/BB ratio in a career-high 179 1/3 innings. For his career, Cobb owns an ERA+ of 111 across parts of six big-league seasons. The 2017 season was his first full campaign since undergoing Tommy John surgery in May of 2015. 

Obviously, he'd give the Cubs a needed dose of depth in a rotation that already includes Jon Lester, Jose Quintana, Kyle Hendricks, and Chatwood. The addition of Cobb would likely allow Mike Montgomery to return to a swing role.