Cueto (elbow) experienced back tightness during Tuesday's bullpen session and is "doubtful" to start against the Dodgers this weekend, Kerry Crowley of The San Jose Mercury News reports.
The Giants had been targeting Sunday as Cueto's potential return date, but things will be put on hold until he's re-evaluated in a couple days. The 33-year-old is about 13 months removed from Tommy John surgery, so the Giants are likely to remain cautious with only a few weeks left in the regular season.