After throwing four pitches to the Arizona Diamondbacks, Greinke was joined on the mound by trainer Stan Conte and manager Don Mattingly. He left the field and retreated to the clubhouse with Conte.
"I think it's minor, but we'll see," Greinke said. "I don't know exactly what it was, but it felt kind of like a cramp."
The Dodgers termed Greinke's removal "precautionary," but even a small injury could push back his season debut. Los Angeles opens its season more than a week ahead of most major league teams with two games beginning March 22 in Australia.
Greinke said he would have continued to pitch with the pain had the strain occurred in the regular season.
"Just trying to take care of it since it's early in spring," Greinke said. "And, hopefully, it's not a big deal."
Greinke caused some ripples in Australia last week when he told ESPNLosAngeles.com he had "zero excitement" for pitching there.
He was careful to clarify his remarks Thursday, saying he had nothing against the country, but was simply concerned about the disruption in his routine. Dodgers and Diamondbacks players voted on whether to take the trip and approved it. Each player will receive $20,000.
Greinke said he voted "no."
"No one wants me to say it this way and my vote if we had to go over there, was not to, but more people wanted to go than not, so now that we are going, I want to be there," Greinke said.
Mattingly said Wednesday that even a small injury could mean that either ace Clayton Kershaw or Greinke wouldn't pitch in Australia.
"It's the reason we've been getting four guys ready, because we know that, at any moment, something like that can happen," Mattingly said. "It's a setback and maybe it changes things. We've tried to get our guys to keep focused on, 'Everybody has to get ready.' Everybody has to be set up for Australia."
Greinke, the 2009 Cy Young winner, was 15-4 with a 2.63 ERA last season for the Dodgers. He missed five weeks after fracturing his left collarbone in a fight with San Diego Padres outfielder Carlos Quentin.
The Associated Press contributed to this report.