The Miami Marlins were expecting to play well enough to contend for a playoff spot in 2015, but right off the bat they knew they would have a difficult time because part of their core was going to be hurt for about half of the season. Ace Jose Fernandez was still recovering from Tommy John surgery and would need to be out until at least mid-June with his ongoing rehab, and that left the Marlins a bit short in the pitching department. Nevertheless, the club knew that would happen and they thought they were well prepared to handle this lone injury problem.
Unfortunately, this was not the only injury situation the Marlins ran into this year, and the team ended up losing a significant amount of playing time from critical players all throughout the year. The Fish lost enough manpower throughout the season that it had to depend on sub-par talent for much of the year thanks to an extreme lack of minor league depth and talent behind its premium players.
There was no better example in how the injury bug damaged the Marlins' chances than in the outfield. The Fish lost Christian Yelich for a combined 25 games to the disabled list. Over the course of the season, Yelich ended up hitting his expected performance marks, as he finished the year with the exact same park-adjusted batting line that he had the last two years. The Fish suffered an even greater loss when they were lost Giancarlo Stanton for a total of 88 games due to a broken hamate bone. Stanton was demolishing pitchers before he left for his injury and was surely meeting his projections from before the season. Had both those players played out full seasons for their team and not missed those games, they may have added around four wins to the Marlins.
The replacements the Marlins threw out there for this combined 113 missed games were the definition of replacement level. Ichiro Suzuki may be a legend who will be returning to the Marlins next year,but he was an awful player in 2015, having hit .229/.272/.289 (.250 wOBA). However, because of injury, he was forced to play a lot; Ichiro logged 438 plate appearances, far more than was expected of him as a backup. The team also threw out Cole Gillespie, Derek Dietrich, and others to try and fill in outfield roster spots in the absence of injured players, along with the extended minor league stay of Marcell Ozuna. In total, Marlins outfielders who were not the three primary starters for the Fish were asked to play a total of 772 plate appearances, and even if you add all of Dietrich's overall performance, their total FanGraphs Wins Above Replacement added up to -0.4 WAR.
The Marlins replaced Yelich, Ozuna, and Stanton with pure replacement play last year, and as a result, they lost four wins directly from injury. But the outfield was not the only location where Miami lost games. The starting pitching staff was depleted severely thanks to offseason trades sending away Nathan Eovaldi, Anthony DeSclafani, and Andrew Heaney away. The Fish traded many team-controlled years of guys who, in retrospect, had strong 2015 showings, and in return the team picked up short-term starting options like Dan Haren and Mat Latos.
However, the problem came when the starters beyond Fernandez also got hurt. Latos missed a possible four starts with continued knee inflammation. Jarred Cosart missed the vast majority of the season, to the tune of 16 potential starts, dealing with the consequences of vertigo secondary to an inner ear infection. This included the time he spent recovering in the minors and his subsequent minor league DL stint for the same problem. Henderson Alvarez spent all of last year on the disabled list as well, as he made just four starts and thus missed 28 potential starts with recurrent right shoulder inflammation. In total, those three Marlins starters missed 48 potential starts, which ZiPS projected to be worth 2.3 wins this season.
Not all of the Marlins' replacements for those 48 starts were terrible, but even some of those guys ended up getting hurt. David Phelps's season ended early with a forearm stress fracture in August. Those who didn't get hurt showed mixed results. The Marlins threw Adam Conley, Jose Urena, Brad Hand, and Justin Nicolino as primary replacements for their missing starters in 2015. Those four guys put up 44 starts and, depending on the system you ask, totaled somewhere between -1.5 to 1.3 wins this season. That means that the Fish cost themselves at least a win by losing out on their expected starters and could have been out up to 3.5 wins on those starts.
In total, one can expect that the Marlins lost at least around five wins this season on injuries alone. The team's replacement-level talent below the surface, due to a lack of organizational depth, cost them in an injury-riddled campaign.