Hairston sounded hopeful that the injury wasn't serious, but manager Don Mattingly gave a gloomier report.
"It doesn't sound very good," Mattingly said after the Dodgers' 4-3 loss in 11 innings to the Cubs. "[Trainer] Sue [Falsone] was saying he couldn't hardly walk down the stairs. Not very good."
Three hours later, Hairston was walking around the clubhouse offering a more optimistic take.
"It felt like a cramp. I hope it's a cramp," said Hairston. "I've pulled and strained the hamstring on my right side and this doesn't feel like that. I hope it's just a mild strain."
If not and Hairston needs to be placed on the disabled list, the Dodgers will recall Justin Sellers, who was optioned Friday to make room for the addition of Bobby Abreu.
Leading off the second inning, Hairston shot a one-hopper that deflected off Cubs pitcher Travis Wood. Hairston made it nearly to first base before pulling up and reaching back toward his left hamstring as he arrived at first base. He was replaced by Adam Kennedy.
The 35-year-old Hairston said he didn't believe the injury was related to the rain delay of more than 2 1/2 hours.
"It's just one of those things," he said. "I did extra sprints to get loose. I made sure I was ready to go. It's a freak thing. Hopefully, I'll be all right tomorrow."
Hairston is hitting .315 and has been playing superb defense filling in for the injured Juan Uribe. This was his 14th game started, eight at third base. He was 6-for-16 during the trip.
The Dodgers' lineup on Sunday was already diminished by the scratch of center fielder Matt Kemp with a tight left hamstring.
Ken Gurnick is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.