Why this rumor makes sense
Miami has always been one of many teams to say it can never have enough starting pitching. Jackson notes the club is still considering Doug Fister, Cliff Lee, Tim Lincecum and Alfredo Simon. The only new name in that group is Simon, but given his history and potential, he fits in.
The Marlins upgraded their pitching staff by adding Chen to complement Jose Fernandez, and have Tom Koehler and Jarred Cosart expected to open the season in the rotation. However, Cosart has been plagued by vertigo and, while he will likely be healthy in 2016, adding depth would likely only prove to be beneficial.
Although the Marlins could have Edwin Jackson, David Phelps, Adam Conley, Justin Nicolino, and Jose Urena compete for the fifth spot in the rotation, adding another veteran might make the starting five that much better. The Marlins are likely hoping to give their prospects additional time to develop and signing another starter would give them the opportunity to do so.
Since Fister and Lincecum did not have a notable amount of success in 2015 and Lee is returning from an injury, none of the three is in a position to request an extensive contract. That should only encourage the Marlins to add another arm.
Why this rumor doesn't make sense
While the Marlins would likely benefit from signing another starter, the club should have enough depth heading into 2016.
Nicolino and Conley both have major league experience, and if the Marlins want to give them additional time to develop, Phelps, Jackson or Brad Hand will likely pitch well enough throughout Spring Training to earn the final spot in the rotation.
Miami's 2016 payroll might not exceed $80 million, but if the organization added another free agent starter, there is a chance it would.
Fister is reportedly seeking a two-year, $22 million deal and the other starters might not be far behind. Given their internal options, the Marlins are unlikely to spend on another starter.
Likeliness overall: 4/10
Miami has starting pitching depth and is unlikely to invest in another free agent starter this winter.