"Matheny is an incredibly tough guy ... but his brain is made the same as everyone else's," said trainer Stan Conte. "He wholeheartedly agreed [to go on the DL], and that tells you something.
"Our biggest concern after a negative CT scan on Wednesday was when to return him to play. He has a mild concussion, but he's had several of those the last couple of weeks. There is a cumulative effect."
The catcher did have blurry vision on Wednesday following that game.
Matheny will get four days of rest, without exertion. In Pittsburgh, the player saw national head-injury specialist Dr. Michael Collins, who gave Matheny short-term and long-term memory tests as well as cognitive tests to determine the concussion's effects.
Rookie catcher Eliezer Alfonzo was recalled from Double-A Connecticut to replace Matheny.
Backup catcher Todd Greene said he's had concussions before, but never from a foul ball.
"He's had a whole lot of them," said Greene of Matheny. "It's amazing how many he's had the last 10 days or so. You never notice that -- the trainer and backup catcher are the only ones who notice.
"The ball picks up speed off the bat. People make a big deal out of people getting hit in the head with a pitch, but we basically get that same effect pretty much daily."
Greene noted Matheny had already been hit several times during the Giants' recent homestand.
"Your head's a funny piece to the machine," said Greene. "You get your brain rattled a couple of times, and it's not like it heals overnight. I'm not a doctor, but I've had enough to know. You have headaches for a few days and think you're all right, then you take two more in the nugget -- that's not good."
The 35-year-old Matheny is a 12-year veteran and a four-time Gold Glove catcher, and he started 44 of the club's first 53 games. He's batting .231 overall but only .114 in the past 10 games.
Matheny was unable to fly out of Pittsburgh due to inclement weather.
Moises nearly ready: Outfielder Moises Alou's sprained right ankle has improved and he may return to play by Monday at the earliest, according to Conte.
"[It's] getting more and more possible," said the trainer, who earlier in the week indicated Alou had reached a plateau and was only around 85 percent healthy. That has changed.
"I would be surprised if it was later in the week. Things like today -- rain and no workouts -- doesn't help us any because we can't get him on the field running. But I was pleased how he was running in Florida."
It's not expected that Alou would play in Minor League rehab games.
"He has such a simple approach to hitting, with a small strike zone, he would have to go anywhere," said manager Felipe Alou. "He stands on the top of the plate and denies the pitcher the strike zone."
Miller bopped: Jon Miller, play-by-play announcer for the KNBR, the Giants flagship station, was wearing a bandage and holding an ice bag on his forehead on Friday night.
Miller was entering Shea Stadium through the Mets' bullpen area during heavy rain and bumped his head in a doorway.
Coming up: Due to Friday night's rainout against New York at Shea Stadium, right-hander Matt Cain will make his Big Apple debut in the first game of Saturday's doubleheader, starting at 10:20 a.m. PT. Cain (3-5, 5.07) will oppose right-hander Orlando Hernandez (3-4, 6.04).
New York left-hander Tom Glavine (8-2, 2.59), originally slated to throw Friday night, will pitch in Saturday's second game vs. Giants right-hander Jamey Wright (5-4, 4.43).