HOUSTON -- Astros infielder Matt Downs has been given permission to miss this week's three-game series against the Nationals to be with his wife, Leah, in Alabama for the birth of their first child.

Downs plans to fly to Birmingham, Ala., following Sunday's game against the Pirates to join his wife, who is scheduled to be induced into labor Monday morning. Downs plans to rejoin the team Friday in Chicago for the start of a 10-game road trip.

"My anxiety is about at a 9.98 on a 10-point scale," Downs said. "But everyone says the first one, you're always nervous. I don't know what to expect."

Downs is hoping his wife doesn't go into labor before he can get to Alabama. If so, he's instructed her to call the cell phone of head athletic trainer Nate Lucero during the game on Saturday or Sunday in case the baby decides to arrive early.

Johnson to get majority of starts at third

HOUSTON -- Astros manager Brad Mills shed some light Saturday on how he plans to split playing time the rest of the season at third base, which has been a rotation between Chris Johnson, Angel Sanchez and Matt Downs the past two weeks.

Johnson, who burst onto the scene last year with a strong rookie campaign, has started just three of the team's last nine games after starting 75 of the first 85 games. Downs has started a pair of games at third during the last nine games, and Sanchez started his fourth game in that span on Saturday.

Mills said Saturday that Johnson will get most of the playing time. Johnson batted .298 in June and is hitting .274 with four homers and 23 RBIs following a woeful April when he hit .185.

"C.J.'s going to get the bulk of it," Mills said. "He got the bulk of it in the first half of the season and he's going to get the bulk of it here coming up pretty quickly. Again, hopefully he's able to get it going, and trying to get these guys some at-bats right now is difficult. He's going to get the bulk of starts as soon as [Sunday], maybe, at third base."

Mills had Sanchez in the No. 2 hole Saturday against Pirates left-hander Paul Maholm, which is the lineup spot where Sanchez has hit during most of his starts.

"[Sanchez] does a good job defensively, wherever you put him," Mills said. "He's done a good job at second and obviously has done a good job at third. We're putting him in there today mainly because how he fits in. C.J.'s struggled against Maholm in the past, even though he's a left-handed pitcher. I think how Sanchez is able to fit into our lineup is nice."

Castro heading to Florida to ramp up rehab

HOUSTON -- Astros catcher Jason Castro will take a huge step in his rehab from the knee surgery he underwent in March when he reports to the Astros' facility in Kissimmee, Fla., next week to ramp up his baseball-related activities.

Castro, who tore his right anterior cruciate ligament during a Spring Training game, has started taking live batting practice and said he plans to shift his rehab to Florida at the end of the homestand. He will be in Florida for about a month and hopes he can return to game action by September.

"I'm looking forward to that, starting to go out there and do stuff everyday," he said. "They have a couple of trainers down there and a physical therapist, and I'll be working with those guys every day and using the facilities and everything to continue hitting and throwing and doing my running progression. I'll continue the catching stuff, too. I'll be able to do more catching-type drills."

As far as batting practice is concerned, Castro said it's going well.

"My knee felt great from the start," he said. "I haven't had any setbacks as far as having soreness the next day after hitting. It's a good sign as far as the health of my knee and my swing and everything."