The Cardinals don't make bad trades often, but they made two in the beginning of 1972 that ruined their chances for the rest of the decade. The worst trade they've made of recent vintage is the Dan Haren, Kiko Calero, and Daric Barton for Mark Mulder deal, in which Haren has won 101 games since the trade. Mulder only won 22 after the trade.
Well, in April 1972 the Cardinals traded young lefty and St. Louis native Jerry Reuss to the Astros for Lance Clemons and Scipio Spinks. Neither Clemons or Spinks panned out and Reuss was one of the better pitchers in the league for the next decade plus. Apparently Reuss was traded because Gussie Busch did not like his moustache and Reuss refused to shave it. Reuss won 198 games(220 total) after the trade, had his last good season in 1988 and hung on until 1990.
The Reuss trade came after an even worse deal in February 1972. Steve Carlton had upset Gussie Busch during contract negotiations a couple years prior and they were about $15,000 apart in 1972. Player salaries back then were not like they are today. Busch had tried to get GM Bing Devine to trade Carlton, but he hadn't yet. Finally on February 25, Devine traded Carlton to the Phillies for Rick Wise.
After the Carlton/Wise deal Tim McCarver(who had caught both in St. Louis and Philly) replied "It was a real good one for a real good one". Carlton was considered to have more ability and stuff and possessed a great breaking ball and was a hard thrower. At the time Wise was considered to be more poised on the mound. At the time of the trade Carlton had 77 wins, three All Star appearances, and was coming off a 20 win season were he had a 3.56 ERA. Wise had won 75 games, made one All Star team, and was coming off a season were he won 17 games and had a 2.88 ERA. Wise was also 9 months younger than Carlton.
Wise actually was a damn good pitcher and won 113 games after the trade and 188 for his career. He started the 1973 All Star Game as a Cardinal and won 32 games and posted a 3.24 ERA in 528 innings in St. Louis. He was then traded after the 1973 season for outfielder Reggie Smith, who was a pretty good player himself. But, Carlton won 252 games after the trade and played for NL East rival Philadelphia until 1986. Carlton also had one the greatest pitching seasons ever in 1972. He was 27-10 with a 1.97 ERA, 0.99 WHIP and struck out 310 batters in 346.1 innings on a last place Phillies team. Carlton ended up with 329 wins and won over 20 games 6 times(5 with Philly). Carlton's last good season was in 1984 and he last pitched in 1988.
In a span of less than two months the Cardinals dealt away 451 wins by trading Carlton and Reuss. Carlton was a dominant Hall of Fame pitcher and ended up winning 4 Cy Young Awards, all with the Phillies. Reuss was more a crafty lefthander type similar to a Jamie Moyer/Kenny Rogers/David Wells type pitcher. However, Reuss was a pretty good 2-3 starter for the Pirates and Dodgers in his prime and helped both teams reach the postseason. Its possible the Cardinals could of won a 2-3 more pennants if they would of kept the lefty pair.
In 1973, the Cardinals finished a game and a half back from the first place Mets. Wise actually outpitched Carlton in 73, but Reuss won 16 games on the Astros and he could of been the difference. The Mets ended up upsetting the Reds and took the A's to 7 games in the World Series that year. They had a strong rotation of Tom Seaver, Jerry Koosman, and Jon Matlack. The Cards would of run out Bob Gibson, Carlton, and Reuss. Who knows what could of happened if they made the postseason?
They also finished a game and a half back from the Pirates in 1974. Rick Wise was traded for Reggie Smith before the season and Wise ended up missing most of 74. However, Smith was one of the Cards best hitters in 74 along with Joe Torre, Ted Simmons, Bake McBride, and Lou Brock. They did have a young Jose Cruz they could of played, but he would of been a dropoff from Smith. The Cards pitching wasn't that strong in 74, Gibson was towards the end of his career and was 11-13 and had a 3.83 ERA and 1.42 WHIP. Lynn McGlothen was their best pitcher and Bob Forsch made his debut in midseason. Their 4-5 spots were weak spots all year. However, Carlton and Reuss both won 16 games in 1974 and having them probably would of won them the division.
There is also the 1981 strike season, in which the owner's decided to have a split season format. The Cardinals finished 1.5 games back from the Phillies in the first half, and 0.5 games back from the Expos in the second half. Overall, the Cardinals were 59-43 which was the best overall record in the division but were screwed out of the playoffs because of this goofy one-time format. This was 9 years after the Carlton and Reuss trades, so its hard to say if they would of stayed around since it was now the free agent era. Carlton and Reuss finished 1-2 in Cy Young Award voting in 1980 and they both had excellent seasons in 1981. The Cardinals bottom 3 spots were a mess in 1981 and the biggest reason why they fell short of the playoffs. In a scenario were both Carlton and Reuss still wear the birds on the bat, they probably win at least one of the half seasons in 1981 and make the playoffs.
From 1975 until 1980 the Cardinals were too far out of it for either pitcher to make up the difference. But, I think its safe to say the Cardinals missed out on at least 2 postseasons because of the these two trades. Gussie Busch did alot of good things as owner of the Cardinals, but these were two bad moments where he allowed a personality conflict to cloud his judgement.