Wells hadn't relieved since he had 20 bullpen outings out of 40 appearances for the Chicago White Sox in 2001.
"I knew it was a possibility these last three or four days," Wells said. "So I've just been trying to stay prepared."
The two innings shouldn't affect Wells' next scheduled start Sunday against the Phillies, who open a three-game series in St. Louis on Friday.
Wells has a 5-0 career record and 1.26 ERA against the Phillies. He had been skipped for his last scheduled start Tuesday.
NOTES AND QUOTES
--Today is the fifth anniversary of the death of Cardinals RHP Darryl Kile, who died in his sleep at a hotel while the team was in Chicago.
--INF Aaron Miles, who had five hits while starting at shortstop Wednesday, "will be in there somewhere" Friday, according to manager Tony La Russa. Lately, Miles has played mostly at short with the back injury to David Eckstein but has seen some starts at second base, too, in place of slumping Adam Kennedy.
--The Cardinals and Phillies are the first two teams to conclude interleague play, with each having played 15 games against the American League. The two teams will have three series with each other rather than the normal two for non-divisional opponents in the National League.
--RHP Tomo Ohka gave up four runs in five innings in his first start for Class AAA Memphis on Wednesday night. RHP Troy Percival, signed earlier to a minor league contract, moved closer to St. Louis with two scoreless innings in the same game.
--3B Scott Rolen hadn't erred in 60 consecutive games over two seasons before he made two errors in his last three games.
BY THE NUMBERS: 1 -- Number of times a Cardinals starter had pitched eight innings, through June 17. RHP Adam Wainwright allowed one hit in eight innings at Kansas City on June 13.
QUOTE TO NOTE: "I was told I could only throw a fastball. That took a little of the fun away. But I did throw one split." -- INF-OF Scott Spiezio, on his scoreless inning of relief in a blowout game at Oakland on June 15.