1. Al Brazle (approximately 12.8 WAR from 1946-1947/1950-1954)
So out of all the great relief pitchers that have pitched for the Cardinals, who has the best wins above replacement? A guy who was never an All-Star, never won a Cy Young, and never won any individual award in his career, go figure. His overall WAR however could be misleading and I'll explain why.
Brazle did not get to the big leagues until he was 29 years old in 1943, recording a 1.53 ERA in 13 games and 9 starts, then he did not pitch in 1944 and 1945 as he served in the military during World War Two. This is where his WAR could be skewed.
In his first year back from war he made 37 appearances and 15 starts, so that is only 22 relief outings. He went 11-10 with a 3.29 ERA so the combination of starts and relief outings would skew his WAR as a reliever alone. Very similar to his starts the next year in 1947, with 19 total starts and 25 relief outings, and just a 2.84 total ERA. Brazle would have more starts than relief outings the next two seasons, but then again in 1950 he had 12 starts and 34 relief outings, how can you accurately predict where the majority of his wins above replacement is coming from? I guess it just depends on who you ask because over those years he was used exclusively as both a starter and reliever.
Brazle was a full-time reliever in his last four seasons in the MLB, starting in 1951 at age 37. He was able to extend his career because of a sidearm delivery that he discovered after dealing with some arm injuries earlier in his career. From 1951-1954 Brazle made 207 relief appearances, went 29-21 with a 3.43 ERA, and broke the Cardinals franchise record at the time in games pitched in a season in 1953 (61). Brazle recorded 48 saves during this stretch as well, including leading all of baseball in 1952 and 1953 with 16 and 18 respectively. In those 4 years, he had a total WAR of 5.7, and his total adjusted WAR if you took a percentage out to recognize the fact that his WAR from a few of those years came from starts, he would still rank towards the top in Cardinals history, just not the highest.
Brazle was a very underrated pitcher, his adjusted ERA is equal to Hall of Famer Rollie Fingers, and it's higher than Hall of Famers Bob Lemon and Warren Spahn and most of his success came way past his prime. Brazles total WAR for his career stands at 21.4, and more than half of that (likely) came as a relief pitcher, it is up for debate on what exactly it should be.