Mulder will throw to Cardinals Minor Leaguers who are still in extended Spring Training, marking the first time in his rehab that Mulder will throw to hitters.
"He's throwing all of his pitches, and they're all going to get better each time he goes out there," pitching coach Dave Duncan said. "He's ready for the next step. He's ready to start facing some hitters and work on execution."
Cards manager Tony La Russa compared what Mulder is doing to what a healthy pitcher does in Spring Training, starting with just throwing, and then progressing to facing hitters before facing hitters in a real game.
"It's a reasonable track," La Russa said. "You can't speed that process up. He can definitely see the progress, and he's excited. That makes us excited."
Mulder threw one last bullpen session in St. Louis on Friday without incident. Duncan said he looked good and threw around 80 pitches.
Mulder underwent left shoulder surgery on Sept. 12, 2006 to repair a partial tear of the rotator cuff.
Welcome back, Randy: The Cardinals made a roster move on Friday to protect their short bullpen when they recalled lefty Randy Keisler and optioned infielder Brendan Ryan to Triple-A Memphis.
Before the move, the Cards were only carrying six relievers. With a doubleheader on Saturday, La Russa said the move was necessary.
"That's a really good move for us," La Russa said. "That will give us some innings and quite a bit of protection. We knew we were going to have to make a move sometime during this homestand, playing four games in less than 48 hours."
Keisler has spent most of the season as a starter. In Memphis, he appeared in 18 games, making 17 starts. He was 8-7 with a 4.43 ERA. The lefty also made three starts with the Cards earlier this season. He didn't receive a decision in any of those starts and posted a 5.65 ERA.
In order to make the move, the Cards had to send down Ryan, who was performing well for the Major League club. In 62 at-bats, Ryan batted .339 and had two homers and five RBIs. The utility infielder, who played second, short and third, made a good impression with the Cards.
"This is a bonus year for him," La Russa said. "He's gotten playing time before it was expected and he's played well. He knows he that he's made a good impression. And every time he comes back, it's another expression of our confidence in him."
Saturday order determined: After wrestling with it for a couple of days, La Russa decided to start Brad Thompson in the first game of Saturday's doubleheader and Anthony Reyes in the nightcap.
"There are arguments both ways, and that's the way we went," La Russa said. "You can go both ways on it."
The Cards will have to make a roster move in between games on Saturday in order to activate Reyes, who had been with Memphis.
Johnson moving on: Lefty reliever Tyler Johnson will also likely head to start a rehab assignment. La Russa said that could come as soon as this weekend.
Johnson will likely just start pitching in games, rather than doing a simulated game or throwing batting practice.
La Russa said he wasn't sure where Johnson would go to start his rehab, but said the reliever threw without pain on Thursday and is ready for the next step. Johnson was unsure also. He has been on the DL since June 19 with a left biceps injury.
Narveson's night: Making his second start for Triple-A Memphis since being activated from the DL with an oblique injury, Chris Narveson flirted with a no-hitter Thursday night. Narveson carried the no-no into the sixth before he was forced to leave the game with a right knee injury. Narveson told the Memphis Commercial Appeal after the game that he didn't think it was anything serious, that he just "tweaked" the knee.
Baby 'Birds: Memphis beat Sacramento, 1-0, on Thursday. After Narveson exited in the sixth, Matt Ginter came on and carried the no-hitter another 1 1/3 innings. Troy Cate eventually allowed a single in the eighth to break up the bid. The Redbirds won in dramatic fashion, when Nick Stavinoha hit a walk-off single off Ron Flores, the brother of Cards reliever Randy Flores, in the ninth to win the game. ... Double-A Springfield beat Wichita, 8-4, on Thursday. Juan Lucena was 3-for-5 with three RBIs. Leadoff hitter Sean Danielson was 4-for-4. Starter Eric Haberer got the win, improving to 10-4 on the season. ... Class A Palm Beach beat St. Lucie, 3-2, in 11 innings on Thursday. Luke Gorsett singled in Isaias Garcia for the winning run. Reliever Donnie Smith picked up the win, pitching two scoreless innings. ... Class A Quad Cities beat Burlington, 14-6, on Thursday. Jamie Landin was 4-for-4 with a homer and three RBIs. Steve Hill was 3-for-4 with four RBIs.
Short-season Batavia beat Brooklyn, 5-3, on Thursday. Jess Todd pitched three scoreless innings of relief and picked up the win. He struck out seven of the nine hitters he faced. Rookie-level Johnson City beat Greeneville, 18-0, on Thursday. Nicholas Vera was 3-for-4 with an RBI and four runs scored. Jose Arredondo and Nicholas Addition combined on a three-hit shutout. Addition didn't allow a hit over the final four innings and struck out six, earning his first save. ... The Gulf Coast League Cardinals beat the Marlins, 4-3, on Thursday. Edgar Lara was 2-for-4.
Coming up: The Cards and Brewers will play a doubleheader on Saturday to make up for a rainout in April. Thompson will face Manny Parra in the first game, and Reyes will square off with Chris Capuano in the second game.
Daniel Berk is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.