Yelich said he felt a tug when he fielded Gregory Polanco's single to lead off the game. The left fielder stayed in the game and bounced out to shortstop in his lone at-bat. He said the best he could move at was half-speed.
Shortly after returning to the dugout, Yelich headed toward the clubhouse, and he was replaced in left field by Reed Johnson in the second inning.
"It feels tight," Yelich said. "I'm not getting around here too fast right now. We'll see what happens. Hopefully I'll wake up tomorrow and it feels better. We're doing everything we can. We'll have to wait and see."
Yelich, batting .259 on the season, is one of the promising young players on the club. On Tuesday night at Texas, he established career highs in hits (four) and RBIs (four) in an 8-5 win.
For much of the season, Yelich has led off. On Friday he was moved to second in the lineup due to the return of Rafael Furcal off the disabled list.
Yelich hasn't dealt with lower back issues before, and he is unclear why he felt discomfort while fielding a routine play in front of him.
"I kind of felt it grab or tighten up after that first hit," Yelich said. "It was kind of just tightening up on me the rest of that inning. I tried to hit. I tried to run to first. Half-speed was the fastest I could go."
The Marlins have been looking forward to seeing how the lineup will function with Furcal and Yelich in front of Giancarlo Stanton.
"It just locked up," Yelich said. "I don't know for what or why. I couldn't keep going. It's frustrating. It's the first time."
Joe Frisaro is a reporter for MLB.com. He writes a blog, called The Fish Pond. Follow him on Twitter