Owen Caissie’s rookie season with the Miami Marlins is essentially over, but the organization appears to view the year as an important first step in the development of one of its key young players.

The Marlins placed Caissie on the 10-day injured list with a lumbar stress reaction after he was removed from Saturday’s victory over the Los Angeles Dodgers because of hamstring discomfort. Further examination revealed a lumbar fracture. With only two weeks remaining in Miami’s season, manager Clayton McCullough indicated that a return for the club’s final series against Atlanta is unlikely.

The injury does not appear to be viewed as a long-term concern. The Marlins’ skipper emphasized that the fracture should heal, although it will require time. Caissie had been experiencing lower-back discomfort that eventually affected his legs, making it difficult to run. He described the issue as different from previous hamstring problems.

“He’s been having some discomfort in the low back for not too long, but it’s been there,” McCullough told the Miami Herald this week. “We knew it was going to be something that we were hoping that we’d be able to just kind of manage throughout the rest of the regular season and knew that it was probably going to be day-to-day and series-to-series with how he was feeling. Yesterday, he just didn’t feel great. ... It was just hard for him to run, and some of the pain got down into the hamstring. “The good thing is that it’s bone,” McCullough added. “It’s going to heal. It’s just going to take some time.”

For the Fish, however, the bigger story is what Caissie accomplished during his first season. Acquired from the Chicago Cubs as the centerpiece of the trade involving Edward Cabrera, Caissie hit .220 with a .700 OPS, 14 home runs, 14 doubles, 58 RBI and 45 runs scored in 108 games.

Those numbers aren't spectacular, particularly for a player whose defensive metrics were also poor. Caissie finished with minus-7 Defensive Runs Saved and minus-7 Outs Above Average in right field. But the Marlins believe there is considerably more potential beneath those numbers.

McCullough pointed specifically to Caissie’s improvement defensively during the second half. His reactions improved, and his athleticism gives Miami confidence that he can eventually become an adequate—or better—outfielder.

Offensively, Caissie learned perhaps the most important lesson of his rookie season: there are no easy at-bats in the major leagues. He must refine his preparation, recognize what works when he's successful, and understand what causes his struggles.

“It’s been a very important and pivotal year for Owen,” McCullough said. “I think his takeaway is that there are just a lot of things that he did that most young players don’t appreciate until they’re here. One, he mentioned defense and how important that really is. He knew he needed to get better, and he still needs to get better, but he did from the midway point of the year until now. [There are] a lot of things under the hood that we believe will allow Owen to be a good defender. His reactions have gotten better. He runs fast enough to be a good outfielder. He’s very self-aware of that."

The Marlins clearly aren't judging Caissie solely by his rookie statistics. They see power, patience, athleticism and self-awareness. His development—particularly defensively and in his offensive approach—could make him a significant piece of Miami’s future.