"Looks like it's a strain," said manager Tony La Russa.
It has become so bad for the Cardinals that utility infielder-outfielder Scott Spiezio, working the eighth inning to give the beleaguered Cardinals bullpen a rest, was their best pitcher. Spiezio walked one and allowed no hits.
The Cardinals have lost six of their last eight games, allowing 72 runs, or nine per game. And La Russa's return to Oakland, where he won a world title with the A's in 1989, was spoiled.
"Very disappointing," said La Russa.
With young right-hander Kelvin Jimenez getting roughed up again in relief, the Cardinals likely will have to reach into their farm system for some bullpen help. They already were looking at bringing up right-hander Anthony Reyes to help the rotation and perhaps move Wells to the bullpen, and now they might have to replace Looper, too.
"It started getting so bad I couldn't get on top of pitches," said Looper. "I thought it was something that would go away ... but in the fifth, it got worse. The best I can understand is that I'm going to see Dr. (George) Paletta on Monday."
The Cardinals are eight games under .500 again but pointing no fingers, La Russa said.
"The club is together," said La Russa, "because we've all taken turns coming up short."
A's 14, CARDINALS 3: The Cardinals' staff allowed six or more runs in an inning twice for the second night in a row. They have ensured themselves of a losing record in interleague play for the second year in succession. Their defeat was their eighth in 10 interleague games this year, and they have been outscored 95-51 in those games with five remaining.