Sean Doolittle spent his entire 11-season career as a relief pitcher. He started with the Oakland Athletics in 2012 and became an All-Star in 2014 when he saved 22 games. Doolittle was traded to the Washington Nationals in 2017 and continued to save at least 20 games annually until 2019.

In 2018, Doolittle made his second All-Star appearance and in the following year, he led the National League in games finished (55) and helped the Washington Nationals win their first World Series. He finished his career with stints in Cincinnati, Seattle, and a second run with Washington, saving a total of 112 games throughout his career.

Robinson Cano, a phenomenal infielder from San Pedro de Macoris in the Dominican Republic, was signed by the New York Yankees in 2001. He made his debut in the pinstripes in 2005 and was the runner-up for American League Rookie of the Year. In the following year, Cano was an All-Star and Silver Slugger after batting .342. He played solidly for the next three seasons and helped the Yanks win the 2009 World Series. Although it was Cano's ultimate accomplishment in baseball, his best individual years were yet to come.

From 2010 to 2013, Cano was New York's best player, winning four Silver Sluggers and two Gold Gloves. He had at least 27 home runs and 94 RBIs in all those seasons. Cano kept his OPS well over .880 over this stretch and was also a perennial All-Star. Despite being a proven superstar, Cano left New York for Seattle in 2014.

Cano remained an upper-tier player for Seattle, earning All-Star spots in three of his first four years and finishing fifth in MVP voting in 2016 when he had 39 home runs and 103 RBIs. However, Seattle was going nowhere, and Cano was traded to the Mets. But at over 35 years old, he was clearly in decline. After an oft-injured 2019, Cano was much better in 2021, batting .316 in the shortened season. However, he lost the entirety of 2021 due to a PED suspension, which raises questions about his performance. Cano limped back with brief stints in New York (NL), San Diego, and Atlanta before quietly exiting the Majors after the 2022 season.

Cano's stats (2,639 hits, 335 HR, 1,306 RBI & 68.1 bWAR) make him worthy of the Hall of Fame. However, the fact that he was suspended twice for performance-enhancing drugs (PEDs) may prevent him from being inducted as no two-time or even one-time PED-suspended player has come close to being inducted into the Baseball Hall of Fame.

Oliver Perez had a long and successful career of 20 seasons in the Majors, playing for eight different teams. He recorded over 1,500 strikeouts, which is an impressive feat for a pitcher who had such longevity in the sport.

Perez had two distinct phases in his career, the first half as a starter and the second half as a reliever. He started his career in San Diego, then moved on to Pittsburgh, where he had an exceptional season in 2003, with a career-high of 239 strikeouts and a league-lead in SO/9 (11.0). He also had his best ERA (2.98) and WHIP (1.163) as a starter. However, he faced some control issues over the next few years. He did have a decent season in 2007 as a New York Met (15-10, 3.56 ERA, 174 K) and fanned 180 the year after. Perez struggled again, and the Mets released him after the 2010 season. In 2012, he made his way back to MLB, this time as a reliever in Seattle.

Perez's performance as a reliever was similarly inconsistent to his performance as a starter. He bounced around from team to team, going from the Mariners to Arizona, Houston, Cleveland, and then Arizona again. During this phase of his career, Perez finished 80 games with 5 saves. He won 74 games against 94 losses, with 1,546 strikeouts.

Despite his impressive career, Perez is unlikely to receive a Hall of Fame vote. However, it has happened before that a 20-year veteran is left off the ballot.

Mark Melancon played for nine different teams in the majors, which may make him seem like a journeyman. However, he was an exceptional relief pitcher and one of the best in baseball at times.

Melancon started his career with New York (AL), Houston, and Boston before having an outstanding season with a 1.39 ERA in Pittsburgh, where he became the Pirates closer. He won the Sporting News National League Pitcher of the Year in 2015, the Hoffman Award, and led the league in saves (51). Additionally, he placed eighth in Cy Young voting that year. Melancon added another All-Star appearance in 2016 when he was traded to Washington during the season.

In 2017, Melancon signed with San Francisco and was later traded to Atlanta in 2019. Although his time in Atlanta was decent, it did not reflect his performance in Pittsburgh. However, he had another fantastic year in 2021 with the San Diego Padres, where he earned his fourth and final All-Star Game appearance and led the NL in saves (39). Melancon played one last year with Arizona and finished his career with 262 total saves.