On January 29, 1971, the Cardinals traded pitcher Nelson Briles and outfielder Vic Davalillo to the Pittsburgh Pirates in exchange for outfielder Matty Alou and a lefty reliever by the name of George Brunet.
The key pieces of this deal were Briles and Alou. The 27-year-old Briles had great deal of success with the Cardinals. He helped the club win the World Series in '67 by posting a 14-5 record in the regular season before locking down a complete game victory in Game 3 of the Fall Classic. The victory was a big one for the series that was destined to go seven games before the Birds celebrated their second title of the decade. Briles returned to the mound in '68 a champion, and he pitched like one by posting a career high 19 wins. After winning 15 more games in '69 things took a turn for the hurler; 1970 was just not his year. He fought through injury, and struggled to the finish line with a 6-7 record. Just like that Briles became expendable. Alou was 32-years-old, and he was a solid veteran hitter who hit .300 or better consistently. The deal seemed to be on that was a good one for both teams.
To analyze this trade in hindsight I would say that Pittsburgh won the deal. Simply put Briles became part of a championship puzzle, as he helped the Pirates win the National League Crown. He went on to pitch a complete game winner in Game 5 of the Fall Classic that had the Bucs prevail over the Orioles in a hard fought seven game battle. Briles pitched three seasons in the Steel City, before being moved to the Royals in '74. While I do believe the Pirates won the deal, I do not think Cardinals completely lost on it either. Alou lived up to his expectations by cranking out a .315 average in '71. Then in August of '72 he was hitting .314 when he was traded to the A's. The trade that sent him packing amounted to virtually nothing for the Birds, while Matty helped the A's charge toward a title.
Alou did wear the Birds on the Bat again. Just briefly in 1973 after he was purchased from the Yankees late in that season. On the other hand, Briles did not return to the Gateway City as a player, but he did pitch until 1978, and even though he left he remained one of many heroes that wore a Cardinals uniform during the late sixties.
Couple sidenotes about the the other players involved in the deal: Davalillo was a platoon type player, and a good bat off the bench. He gave the Bucs two solid seasons before watching his numbers tail off. George Brunet spent 15 years in the big leagues. He made just seven appearances with the Birds before being released in May of that year. Interestingly enough Brunet's career in baseball extended all the way until 1989. His days on the diamond as a professional began in 1953. After the Cardinals released him he bounced around the minors before heading to Mexico where he set multiple records, and pitched until he was 50 years of age. You can read a great piece about him here: http://www.hardballtimes.com/cooperstown-confidential-the-wild-life-of-george-brunet/