"It is a little strange, but you have to remember we're an older team and we're approaching 100 games," Houston manager Cecil Cooper said.
Berkman, who walked in the ninth inning Saturday as a pinch-hitter, said Sunday his calf hadn't improved enough for him to play. He said he could feel the injury when he walks and is eager to rejoin the lineup, especially with the first-place Cardinals coming to Houston on Monday.
"Cardinals or not, they're paying me a lot of money to play, so as soon as I think I can get out there, I'm going to get out there," he said. "Certainly, that's an important series for us and I'd like to be able to play."
Berkman has never had an injury like this before and was more than willing to take trainers' advice not to play Sunday. He said if the injury doesn't improve by Monday he would like to get some tests run to help gauge the severity of the problem.
"They haven't told me that, but I'm going to request it," said Berkman, who leads the team in homers, RBIs, slugging percentage and on-base percentage. "If it doesn't start feeling better, I want to know what's going on."
Erstad, who strained his hamstring in the eighth inning Saturday met with Cooper and general manager Ed Wade after the game to talk about the severity of the injury.
"We asked him to be candid with us, and if he thinks it's something that's going to linger then we can shut him down and address it," Wade said. "We have to monitor and ask him to be up-front with us."
Erstad called the injury "very frustrating."
Matsui, who has four multiple-hit games in his past five starts, was out of the lineup Sunday in part to get him some regular rest but also because of his hamstring. Matsui missed 18 games on the disabled list earlier this year with a left hamstring strain.
"It's a little bit odd coming out of the All-Star break," Wade said of the rash of injuries. "There were days of airline travel and more airline travel and honey-do lists, so I'm not sure anybody spent three days in a horizontal position resting up. But it's nicks and dents and nothing profound."
Meanwhile, relief pitcher Doug Brocail will begin his Minor League rehab assignment Monday at Triple-A Round Rock. Brocail, on the disabled list since May 4 with a left hamstring strain, will throw twice at Round Rock and four times at Double-A Corpus Christi before hopefully rejoining the team.
"I feel I need a lot of work," Brocail said. "The fastball is not where I want it to be, control is not where I want it to be. You throw some fastballs that have a little bit of giddy-up and throw some where you try to make a good, hard fastball, and I'm actually cutting it off a little bit. As far as mechanics, I have a lot more mechanical work than I do worrying about the leg."
For Brocail, 42, the next two weeks will essentially be like Spring Training.
"Even though I've been throwing bullpens, bullpens aren't the same," he said. "You don't have the intensity level, you don't have the same scope as far as being able to dot your I's and cross your T's as far as hitting your spots. It's a lot easier with a guy in there. You have something to throw to."