When the Miami Marlins acquired Dan Haren, it was with the express knowledge that he may choose retirement over moving temporarily to Miami. Haren had previously expressed the sentiment that he would prefer to stay on the west coast and play for either the Los Angeles Dodgers, Los Angeles Angels. or San Diego Padres, and that he would retire if he were not afforded that option. Miami still took him and the Dodgers' $10 million in salary relief anyway. At the time, it seemed not unreasonable, as the Fish could flip Haren and keep the $10 million in savings anyway, likely to be invested elsewhere.
However, that was when the Marlins were flush with starting pitchers. They still will be flush with Major League-quality arms once Jose Fernandez returns from injury, but that will be in midseason around July. Until then though, the Marlins will have to turn to some replacement-level arms to assist in the fifth starter spot if they are forced to trade Haren or if he chooses retirement.
Haren has not been a great pitcher over the last three years. Since a dominant six-win campaign with the Angels in 2011, he has posted an ERA of 4.33 and a FIP of 4.14 over the past three years, but he has also made more than 30 starts in each of those seasons. His worst year was last season, but even that campaign was worth around one win over the course of the enitre year. FanGraphs has him worth 4.2 wins in three seasons, while Baseball Prospectus has him at 3.8 wins. Steamer has a good projection for him next year, with an ERA actually less than 4.00 moving to Marlins Park and a total of 1.6 wins in 160-plus innings.
While this may not be exactly accurate, it would not surprise me to see Haren succeed in Miami. His issues in the last three years have all been associated with the home run, as he has allowed a staggering 83 homers since 2012. That number is the second-most number of homers out of any qualified big-leaguer since 2012, behind only R.A. Dickey. But Haren's other numbers actually remain fantastic. Last season, he posted his lowest strikeout rate at 18.7 percent and still had low walk rates at 4.8 percent. Since 2012, Haren's strikeout rate minus walk rate is 31st in the league. Those underlying peripherals are still good, but his problem with allowing too many homers is plaguing his game.
Even if all of those things persist for most of next season, Haren should still be an acceptable player. But if his home run rate drops moving into the cavernous outfield of Marlins Park, the Fish may have a nice trade target for midseason or even a competent fifth starter to replace an incumbent guy once Fernandez gets back. Because Haren's downfall has a lot more to do with home runs than his other base skills, Miami has some surprising upside in keeping Haren around if he is willing to pitch.
If Haren is not willing to come to Miami, though, then the Marlins will find some issues instead. On the one hand, the team will either get nothing but money in return for Haren or may face a situation of getting very little in trade value back. According to some sources, Miami may consider one of the Padres' cadre of outfielders, While picking up Will Venable may not be a terrible idea for a fourth outfielder (Miami currently has no one who can play center field on the bench), that player would not have nearly the effect that Haren could produce out of the fifth spot and potentially for an entire season. There is no guarantee the Marlins' triplet of amazing young outfielders can stay healthy all year, but the suspicion is that the backup outfielder may only long 200 plate appearances as a whole.
As for the team's replacements, Miami will have to turn to David Phelps, Aaron Crow, or Brad Hand for that final spot. Hand has already shown himself to be mediocre; he owns a career 4.42 ERA and 4.76 FIP, both of which are greater than 15 percent worse than the league average. Crow is coming off of his worst season as a reliever and may be converted to a starter despite having not started since 2010 in the minors. Phelps figures to be the most effective of the three, with a career ERA and FIP of just around four percent worse than league average. He may be the eventual choice at fifth starter, but all three choices would be inferior to Haren. It is likely that, within half a season, Haren would be at least half a win to a win better than these guys, depending on what you see in terms of upside in his game.
This is a small impact in half a season. It is possible Phelps would come closest to providing similar numbers. But for a Marlins team that fancies itself close to contention this year, every small advantage counts. The club probably gained a small number of wins this year in trading Nathan Eovaldi for Martin Prado, but if Haren does not want to stay, the Fish may give back that advantage.
What is the solution? There are no mid-tier starters left in the free agent market, as the only remaining names are low-impact non-upgrades, one injury-upside guy (Chad Billingsley, who essentially hasn't pitched in two years), and the top two remaining starters in James Shields and Max Scherzer. The Marlins could remove Haren from their roster while keeping the Dodgers' money and attempt to pursue Shields, but he may be out of the team's price range at this point. Outside of that, there are no real strong upgrades to solve the Haren half-win problem. It may just be something Miami has to live with.