Jason Heyward
In 2010, a 20-year-old named Jason Heyward dominated the Grapefruit League and made it impossible for Bobby Cox to keep him off the Opening Day roster. In his very first Major League at-bat, he did this:
Heyward finished second in Rookie of the Year voting, was an All-Star, and looked like his name would be mentioned alongside Hank Aaron, Eddie Mathews, and Chipper Jones when talking about the greatest Braves of all time.
Unfortunately, that didn't happen. Although Heyward's had a solid MLB career, he's been far from the greatest. His Braves tenure ended after the 2014 season when the club shipped him off to St. Louis in exchange for Tyrell Jenkins and Shelby Miller. As a Brave, Heyward averaged nearly 4.0 fWAR per season, although much of that value came from his outstanding glove.
The lefty had a solid season with the Cardinals and parlayed that into an eight-year, $184 million contract. During his seven seasons, he only had a wRC+ above 100 once, and it was during the shortened 2020 season. He was released after the 2022 season, joined another player on this list out in LA, and had his best hitting season since he was a Cardinal.
Among the players on this list, Heyward certainly had the highest expectations, and while playing 14 MLB seasons is certainly an accomplishment, it's easy to argue that his career has been somewhat of a disappointment.
Craig Kimbrel
The Braves first called up Craig Kimbrel in May of Bobby Cox's final year. The righty went up and down several times, but was brought up for good in September. On the entire season, Kimbrel was excellent in the 20.2 innings he pitched, striking out 40 batters and only allowing one run.
Cox turned to Kimbrel in the postseason after Billy Wagner went down with an injury, and unfortunately the Braves couldn't win either game he appeared in the 9th.
The following season, Kimbrel continued his dominance and took home the Rookie of the Year. Alongside Eric O'Flaherty and Jonny Venters, the trio headlined one of the most unstoppable bullpens in baseball.
The flame-throwing closer is still the franchise leader in saves but his tenure with the Braves ended shortly after Heyward's. Although he was with the Braves in Spring Training of 2015, the club traded him along with B.J./Melvin Upton to the Padres in a prospect package that also included the pick that became Austin Riley.
Since leaving the Braves, Kimbrel has played for the Padres, Red Sox, Cubs, White Sox, Dodgers, and Phillies. He is currently on the Orioles roster for the 2024 season.
Despite his journeyman nature, Kimbrel has remained a somewhat elite reliever. Last season, he became eighth player in MLB history with 400 saves, which he unfortunately accomplished at the Braves expense in Atlanta.