Kershaw left in the second inning after throwing 21 pitches after he was checked out by trainers. The Dodgers went on to win the game 5–4 in 10 innings.
"A lot of frustration," said Kershaw. "I've done countless hours of back maintenance and rehab just trying to stay healthy and felt really, really good up to this point. There's definitely frustration, for sure."
"He wasn't feeling anything before that warmup," Dodgers manager Dave Roberts said. "From what I understand it's more muscular. That sharpness from the herniation is not what he felt today. The scans could prove different. That's all I got on that."
Kershaw, who missed 2 1/2 months last year with a herniated disk in his lower back, is 15–2 this season with a 2.04 ERA, 0.88 WHIP and 168 strikeouts in 141.1 innings.
The Dodgers have won 33 of their last 39 games and have baseball's best record at 68–31.