The move came less than a week after St. Louis failed to sign Mike Hampton, who agreed to a $121 million, eight-year contract with the Colorado Rockies.
"Entering the offseason, we felt that we needed to improve our pitching in order to improve the ballclub," Cardinals general manager Walt Jocketty said. "After seeing once again how unsettled the free agent market can be, we turned out attention to the trade route something that has worked well for us in getting value for value."
Hermanson, 27, was 12-14 with a 4.77 ERA in 30 starts and eight relief appearances with the Expos last season. He has a career 47-48 record and 4.17 ERA in 170 games, 122 as a starter.
Hermanson won a career-high 14 games in 1998 with a 3.13 ERA. He has struck out 559 batters in 805 career innings, walking 292.
Kline, 28, fills a void for a quality left-handed reliever. He had 14 saves in 18 chances while serving as the Expos closer for three months this year. He went 1-5 with a 3.50 ERA in 83 games, leaving his career record at 15-19 with a 3.84 ERA.
Both are signed through the 2002 season with club options for 2003.
Tatis, who on March 11 agreed to a $15 million, four-year contract. is the first player to hit two grand slams in an inning, accomplishing the feat in 1999 at Los Angeles. He hit .298 that season with 34 homers, 107 RBIs and 21 stolen bases.
Tatis started strong this year, batting .375 with 28 RBIs in April. But he tore a groin muscle in a game at Philadelphia and missed 54 games and hit just .204 upon his return.
He struggled so badly that he was benched for much of the postseason in favor of Placido Polanco. Tatis wound up hitting .253 with 18 homers and 64 RBIs.
He also struggled defensively in the postseason, committing two costly errors in a Game 4 loss to the Mets in the NL championship series after making only eight errors during the regular season.
Reames, 27, was thought to be an possible starter for the Cardinals next season. A rookie this year, he replaced the injured Andy Benes for a month at the end f the season. He was 2-1 with a 2.86 ERA for eight games, then pitched 9 2-3 innings in the postseason, giving up just one run.
He replaced fellow rookie Rick Ankiel in Game 2 of the NL championship series, allowing one run in 4 1-3 innings. He was a possible pick to start Game 6, but the Cardinals lost in five games to New York.
"Giving up Tatis and Reames was difficult," Jocketty said. "However, we do feel we have enough depth within the organization at third base ... Everyone knows that Reames was an important part of our playoff team last year, but in order to get Kline, we had to include him in the deal."
Polanco and Craig Paquette likely will share duties at third base next season. One of the Cardinals' top minor leaguers, Albert Pujols, is a third baseman but is probably a year away from the major leagues.
Pujols, 20, moved from Class A to Triple-A in his first professional season. At Class-A Peoria, he hit. .324 with 17 homers and 84 RBIs.
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