Manager Mike Redmond wasted little time getting Morrison in the lineup, starting him at first base and hitting him fifth.
"It worked out that LoMo was available and ready to go," Redmond said. "I know he's excited to be here, and we're excited to have him. Hopefully, he will be a nice lift to our lineup, and a boost to the team."
In the eyes of the organization, Morrison is a big addition to the lineup. He offers a potential left-handed power bat to the middle of the order.
"This is what I do," Morrison said. "I'm just here to help the team and be part of the team. Give these guys energy. I know they're struggling a bit."
Coghlan, who started in center field on Saturday, was replaced after eight innings. The Marlins went on to beat the Mets, 2-1, in 20 innings, which matched the longest game in franchise history.
"My muscle is not firing in my calf," Coghlan said.
Coghlan has been playing through discomfort in the calf for about three weeks, and on Monday in Miami he will have an MRI.
"We had to put him on the DL, he's a little banged up," Redmond said. "We were hoping he was going to be able to fight through it -- he tried. It's definitely not the situation he wanted or we wanted. We've got to get him healthy."
From the early innings on Saturday, Coghlan was in pain, and it worked out that he could be part of a double-switch after the eighth inning. Justin Ruggiano played center the rest of the game, and started there on Sunday.
"I wasn't moving great the whole game," Coghlan said. "It was one of those things where I was trying to get through the game, but it was just too much pain."
Coghlan said he was told the discomfort could be sciatic nerve related, but more will be known after the tests are taken.
"I need to get tested and find out what it is," Coghlan said. "I don't feel anything in my back, it's all in my calf."
At the time Coghlan was exiting Saturday's game, Morrison was playing in his final rehab assignment game with Double-A Jacksonville. The left-handed-hitting first baseman had one at-bat on Saturday night before being pulled from the game in Birmingham, Ala.
Morrison was up at 5:15 a.m. ET, and traveled to New York. He had been monitoring the Marlins' marathon with the Mets, and he sent a light-hearted text message to Redmond.
"I sent Red a text, joking with him before I knew I was coming up here, 'I guess I'm flying up tomorrow to New York to pitch, too?'" Morrison said. "They called and said I'm going to New York tomorrow. I was like, cool."
Morrison is returning to the big leagues for the first time since July 28, 2012. He missed a bulk of last year due to a right knee injury, which required surgery in September.
While on his rehab assignment, Morrison played in 16 total games, including 10 at Jacksonville. He had 56 total at-bats, and batted a combined .179 with two home runs and 10 RBIs.
The Marlins had been planning on reinstating Morrison on Monday, when the team opens a three-game set with the Brewers at Marlins Park.
Coghlan's injury comes at a time he was one of the team's hottest hitters. The 2009 National League Rookie of the Year Award winner is batting .277, including a .338 mark with a .379 on-base percentage since May 1.
Prior to the injury, Coghlan was in the process of going through a transition to third base. The plan was to give him extensive work at third next week when the club returned to Marlins Park.
After being away from the big league club for about 10 months, Morrison has a bigger appreciation for being back.
"I think there will be a lot more smiling," Morrison said. "It doesn't matter if I'm 0-for-4 or 4-for-4, I'm probably going to have a smile on my face today. … I'm here and ready to go, and I appreciate it a lot more. It's like I just got called up again, and I'm ready to go."