As reported by multiple sources but first mentioned by MLB.com's Joe Frisaro:
The Marlins are sending down Chris Coghlan and Michael Dunn, both of whom have disappointed to start the season, and are bringing up two fresh faces in lefty reliever Dan Jennings and outfielder Bryan Petersen. Coghlan had been struggling to start the year, batting just .121/.147/.152 in 35 PA to start the year. Dunn has similarly struggled in the small sample that is the 2012 season, allowing a 5.40 ERA despite decent peripherals in five innings pitched before today.
It is difficult to put much blame on either Coghlan or Dunn, though Dunn's struggles with batting average on balls in play (.468 before today's game) certainly did not help. When you look at his numbers, his strikeouts have jumped out, and his walks are not all that disappointing, especially since two of the four before today were unintentional. Of course, Dunn participated in being one of the four pitchers to walk four consecutive batters, so he has some infamy behind his walks, but his play overall has just been mired by a combination of likely bad luck and some poor pitch placement. Now, having said that, those could also be due to poor pitch location, as Dunn has only put 43 percent of pitches thrown into the zone, so it does not hurt to send him for a tune-up in the minors.As for Coghlan, it seemed like the right call to have him start in the minor leagues from the start of the season. Coghlan has missed a significant amount of playing time with injury and has been shifted around to learn multiple new positions. What he may benefit most from is simply more reps, and no matter how Guillen balanced his playing time, Coghlan was certain to lose time at the plate and on the field. This way, he can get a lot of playing time and try and rebuild his career to some degree after the last two years have ended in disappointment.
Dan Jennings is the reliever the Marlins have coming up, and like Dunn, he is a lefty. However, the similarities pretty much end there. Jennings is a low-90's thrower with a fastball and slider combination that induces a lot of strikeouts from lefties but misses the plate a good deal as well. If batters do get the ball in play, they tend to hit it on the ground; he has posted ground ball rates over 50 percent at each stop since 2009. In that respect, he is more closely associated with lefty specialist Randy Choate rather than Dunn, but Jennings does have some tools to face right-handers, so he may be taking a seventh-inning lefty role opposite Steve Cishek's righty role.
Bryan Petersen hit .265/.357/.387 in 241 PA last year after Coghlan was demoted and later placed on the disabled list. This made it extremely interesting that the Marlins decided not to continue with Petersen as their backup outfielder, especially given his decent reputation defensively. The Marlins will have Petersen back up all three outfield positions with his patient, walk-heavy, power-light approach. At this point, this sort of approach would be better than using Coghlan's worse plate discipline and similar weak power.
Neither of these two moves will improve the Marlins significantly, but it does not mean that they are not correct moves. Both players in the big leagues were struggling, and they were expendable pieces given the presence of similar options. Dunn can work on his locations and Coghlan on his defensive reps in the low-pressure minor league situation, while the Fish gain a little more defense and do not lose anything significant on the pitching side.