He missed Sunday's start against San Diego. On Tuesday, he threw a bullpen session, with manager Bruce Bochy even stepping into the batter's box, and the left groin injury was not an issue.
"I was throwing everything like I'm pitching in a real game, and I noticed nothing was bothering me," Cueto said, according to the Mercury News.
Bochy said that Cueto will go through some fielding work on Wednesday as a final check of the injury. If all goes well, he will start Thursday against the Rockies without restrictions.
A healthy Cueto is key for the Giants, who are clinging to the second wild-card spot in the National League.
Cueto (17-5) was forced out of his start Sept. 20 in the sixth inning because of the injury.