ST. LOUIS — Albert Pujols prevented Jason Isringhausen's latest failure from hurting the St. Louis Cardinals.

Pujols hit a game-winning single in the ninth inning after Isringhausen allowed a tying home run to Jose Hernandez in the top half, giving the Cardinals a 4-3 victory over the Pittsburgh Pirates on Wednesday and a three-game sweep.

Pujols, who leads the majors with 29 RBI, has the game-winning RBI in four of the Cardinals' last five victories.

"Izzy, I know he wanted to get that save right there, and he made a mistake," Pujols said. "But we came out with a win, and everybody will forget about what happened."

St. Louis led 3-2 with two outs in the ninth when Hernandez hit his first homer of the season. Isringhausen (1-2) has allowed three homers in eight innings this year, two resulting in losses, and has a 6.75 ERA.

The Hernandez homer denied Mark Mulder his 100th career victory. Then, in the bottom half, David Eckstein and Hector Luna hit consecutive singles off Roberto Hernandez (0-1), and Pujols lined a 2-2 pitch down the third-base line.

Pujols was down 0-2 earlier in the count.

Hernandez thought he had Pujols struck out on an 0-2 pitch.

"If he doesn't swing 0-2, it's not a strike," Hernandez said. "He's such a great hitter and such a great competitor, anyway, and now you consider him like Barry Bonds, when he was going good."

Luna, who went 2-for-5 and raised his average to .432, had his fourth straight multihit game for the Cardinals, who have won six of seven overall. They're 29-10 against the Pirates since 2004 and swept them for the first time since May 23-25 last year.

Juan Encarnacion, batting cleanup for the first time this season, hit a sacrifice fly in the fifth off Zach Duke to break a 2-2 tie. Encarnacion has five RBI the last two games after totaling one in the first 19.

Craig Wilson hit a two-run homer in the fourth for the Pirates, who have a season-worst seven-game losing streak. They've been outscored 34-12 during the slump, have lost 12 of 13 on the road and are an NL-worst 5-18.

"We've had a few like this," manager Jim Tracy said. "The record may suggest differently, but when you look at the games we've played, we've had our fair share of games like this."