OAKLAND -- The A's have gotten used to seeing Jarrod Parker get better and better.
Saturday was, by all accounts, Parker's best yet, this from a pitcher who had gone 5-1 with a 2.59 ERA in his last nine games. But a hamstring injury forced him out of his start against the Cardinals in the fourth inning, and St. Louis won 7-1 behind 11-game winner Adam Wainwright.
Wainwright had a shutout going for seven innings until a double by Josh Donaldson and an RBI single by Josh Reddick got Oakland on the board in the eighth.
The quality of Wainwright's stuff served to underscore how important Parker is to the A's. They believed Parker capable of matching Wainwright pitch for pitch. Parker had allowed just two base runners when he collapsed in front of the mound holding his right hamstring after giving up a two-out double in the fourth.
"The way Jarrod was throwing," Donaldson said, "if he could have stayed in there, we might still be out there with the score 0-0."
Parker wanted to stay in the game. He got up, with trainer Nick Paparesta and manager Bob Melvin hovering nearby, and made a few throws to the plate. When Parker said he could still feel the hamstring, Melvin told him he was through for the day.
And that was a shame, because Wainwright was throwing great, and Parker wasn't taking a back seat.
"Honestly, that's the best I've ever seen him throw," catcher Derek Norris said. "He threw everything, his velocity was the best ever, and the movement on his pitches was great. I feel bad for him that he had to come out of the game. It was his best effort."
Now the A's have to hope that the problem was just a heat-induced cramp. The announced temperature at the first pitch was 84 degrees, a season high at the Coliseum, but the game was playing warmer on the field. The next 24 hours will tell if it's a cramp or something more serious.
"I've never had leg issues before this," Parker said. "But we'll figure it out. Tomorrow will be a big day."
The A's are hoping to be able to determine Sunday if the problem is, indeed, a cramp. If so, Parker could be expected to make his next start in the final game of the Cubs' series in the Coliseum next week.
When Parker tried to stay in the game after throwing a few trial pitches, he said he did not argue as stridently to stay in as he could have.
"I felt all right," he said, "but it probably would not have been the smartest thing to do to stay out there."
Even Parker said that he would have liked to have seen the Wainwright-Parker matchup play itself out.
"His tempo was great," Parker said of Wainwright. "The first three innings flew by for both of us. We were looking to emulate and repeat."
The innings kept flying past for Wainwright, who went on to throw his fourth complete game of the year, the best in the National League. For the A's, the pace slowed. Jesse Chavez, the hero of the 18-inning win over the Yankees on June 13 when he threw 52/3 shutout innings, was asked to contribute another long scoreless outing.
This time, it didn't happen. He pitched out of the fourth, but he opened the fifth with a walk and a hit batsman, and both runners scored. Two hits opened the sixth, and he was out of the game. Reliever Jerry Blevins was hit immediately, giving up an RBI single to Matt Holliday and the first of two Matt Adams homers.
If Parker can come back by Thursday, the A's will consider themselves lucky.