Overall, the bullpen was a strength for the Marlins last season. However, it was way overused due to the inconsistency of the rotation. This is the main reason why the front office set out to acquire starting pitching this offseason, which they achieved by adding veterans Mat Latos and Dan Haren to an otherwise young rotation. Although James Shields slipped through the net (even though the Marlins reportedly offered more money than San Diego), the Marlins' rotation has been greatly improved from 2014.
Henderson Alvarez produced an All-Star campaign last season and he will be heavily relied upon to produce similar results this year. This shouldn't phase him as he spent most of 2014 as the team's ace and stepped-up accordingly. Alvarez projects to be the opening day starter, and if he can produce anything near his impressive 1.60 home ERA in 2015, he can lead by example and the Marlins will be moving in the right direction. Predictably, Henderson Alvarez's ZiPS projections have his numbers regressing back towards his career averages, but there is no reason not believe that he will continue to improve in his third season with the Marlins.
If Mat Latos recaptures his 2013 form, he could form a formidable 1-2 duo with Alvarez and then the Marlins would arguably have two ace-caliber pitchers in their rotation. While Latos' 2014 season wasn't too bad statistically, it was an injury-filled campaign, and the Marlins cannot afford any setbacks if they want to keep up with the rest of the National League. The Marlins traded for him because of the durability he was known for before last year, and they are banking that he can pitch over 180 innings again in 2015 and bring consistency to the rotation.
A recent article on Marlin Maniac stated that Jarred Cosart is a very important arm with regard to how the Marlins fare this year, and this is true. The team got more than they could have hoped for when they received Cosart in a trade from the Astros last summer, as he posted a 4-4 record and a 2.39 ERA with Miami. Although not all of his performances were impressive, if he can improve this season at the rate he did over the course of 2014, then the Marlins should have a solid number three starter.
Dan Haren is the big question mark hanging over the starting rotation. He has now committed to pitching for the Marlins this season, but is his heart in it? Is he playing because he still believes he can perform at a high level, or is he just wanting to earn his $10 million dollars? If he is on board with the team's aspirations and is determined to make an impact, then Haren should be able to log some significant innings for the Marlins while hopefully posting a sub-4.00 ERA and providing some vital wins.
Based on his dependable performances last season, Tom Koehler should be called upon to round-out the rotation. He threw the most innings out of all Marlins pitchers last season (191.1) and the team will need similar numbers from the starting pitchers this season if they want to remain competitive. If Koehler's 2014 numbers are anything to go by, then the Marlins should have an above-average fifth starting option.
For the Marlins, 2015 will be a tale of (roughly) two halves. The first half will be trying to remain in the hunt before June 15th; the second will be aiming to play late-October baseball. This will be made possible by the best midseason acquisition of 2015 (if things go accordingly) - Jose Fernandez. June 15th is when the Yankees come to town and you can bet that if Jose is ready, he will pitch in that game. The rotation must hold up until that date though, otherwise the playoffs could already be out of reach. The only way the rotation can have success is if the starters pitch deep into games. June 15th will be a big day if Jose Fernandez returns for the Marlins. It will signify new beginnings, and a new chapter in the book of the 2015 season, a book that hopefully ends with the Fish on top.