Infielder Juan Castro was designated for assignment.
Ramirez, out since July 17 with a strained right calf, went 0-for-3 with two strikeouts in the Dodgers' 8-5 win over the Reds. He played five innings in left field before yielding to Reed Johnson when the Dodgers' lead reached six runs.
Prior to his activation, Ramirez went a combined 1-for-6 with five strikeouts in three rehab appearances for Class A Inland Empire, the most recent on Friday. Those aren't numbers that indicate he's found his timing.
But at this point, with the Dodgers one loss away from falling to .500, having Ramirez find his way on the fly is the best option they have. The Dodgers are averaging 3.09 runs per game since Ramirez has been gone, tying the Mets for worst mark in the Majors.
"Am I expecting him to be sharp? Not necessarily," manager Joe Torre said. "But he knows how to hit."
"He's probably stronger and better now than when he left. I don't know if his timing is as good," said the Reds' Dusty Baker, who's managing against the Dodgers this weekend. "If Manny is playing well, he can beat you by himself."
Torre said he would talk to Ramirez in the sixth or seventh inning Saturday to see how he feels, and that the 38-year-old would not play in Sunday's day game after a night game -- something he would normally skip anyway.
But the Dodgers don't think they'll have to be too careful with Ramirez, because they're convinced he's healthy this time -- or at least more convinced than they were the last go-around. Ramirez had been on the DL two times previously this season, once for another calf injury, once for a hamstring injury, all in the right leg. He's missed more than half of the season.
The last time Ramirez tried to come back, right after the All-Star break, he couldn't make it through two games. He was pulled from left in the bottom of the first inning in St. Louis on July 16.
"That's certainly something that's fresh in our mind," Torre said. "You have to pretty much leave it to him. It's his body and he know he feels. Am I curious, am I going to hold my breath? Yeah, probably, a couple of those things ... but you're really running out of rehab time anyway, with the Minor Leagues coming to a close in the next week or so."
Team trainer Stan Conte watched Ramirez personally at the team's Spring Training complex in Arizona at the start of the week, and said he put Ramirez through the rigors.
"We timed him on the bases, we made him run hard, and he had no problems then, no soreness, and he was able to play in San Bernardino the next day," Conte said. "Now, anybody can get a pulled muscle at any time."
Ramirez has hit .317 with eight home runs and 39 RBIs in 186 at-bats this season, and he allows the Dodgers to break up the lefty-lefty tandem of Andre Ethier and James Loney.
Jay Gibbons batted fourth behind Ramirez on Saturday, his first game in the same lineup as Ramirez. But Gibbons remembers the damage Ramirez can do well: Gibbons was with the Orioles for seven seasons while Ramirez was with the Red Sox.
"Manny was the best right-handed hitter I've ever played against," Gibbons said. "No question. He was an incredible player. He still he is."
As long as he's healthy.
"He said, 'I'm ready to go now,'" Torre said. "Only way we're going to find out is send him out there and see what we see."
Though the Dodgers have not officially declared themselves sellers, Ramirez's return before the end of the month leaves open the possibility that he could be placed on waivers and finish the season with another organization: either by trade, or if another team claims Ramirez and the Dodgers let him leave to save money.
Evan Drellich is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.