Coghlan was placed on the 15-day disabled list with right calf nerve irritation last Sunday. An MRI exam on Monday revealed what the Marlins now believe is a lower back strain.
The uncertainty surrounding the 2009 National League Rookie of the Year's injury has resulted in him being sidelined indefinitely. Coghlan, who has not played since June 8, initially believed his injury was only a minor setback.
"I was a little bit surprised it was a little more serious than what I thought," Coghlan said. "I thought I'd be back in two weeks, and I don't think it's looking like that so far."
Coghlan's injury could potentially take a substantial chunk out of arguably his best season since 2009.
He had been trending upward since earning a spot in the everyday lineup, batting .343 (23-for-67) with four runs and nine RBIs in 73 plate appearances since May 18.
Coghlan credited his resurgence to simply receiving more playing time.
"The first day, I was really bummed," Coghlan said. "I was upset, frustrated and bummed. And then after pouting about it for a couple of hours, I was like, 'All right, I've got a choice to either continue pouting and feeling sorry for myself or grind through this deal.'
"So, I've change my mindset and my attitude. This is what it is. There's nothing I could've done to prevent it. It's something that happened, and I've just got to get better and get back on the field as soon as I can."
Joe Morgan is an associate reporter for MLB.com.
This story was not subject to the approval of Major League Baseball or its clubs.