Melancon graduated from Golden High School in Colorado where he played baseball, basketball, and football. He was then drafted by the Los Angeles Dodgers, but chose to attend the University of Arizona.
Mark has recorded 168 career saves entering 2017, reaching a personal best with a Major League-leading 51 in 2015 with Pittsburgh. He has converted 98 of 104 save opportunities in the past two seasons and is coming off a 2016 campaign for the Pirates and Nationals in which he recorded a 1.64 ERA and 47 saves in 51 chances over 75 games. Signing a four-year contract with the San Francisco Giants on December 6, 2016, Mark has recorded 147 saves with a 1.80 ERA and a 0.91 WHIP since the outset of 2013. The righty was brilliant again in ’16, holding opposing hitters to a .204 average and blowing just four of his 51 save chances. A three-time All-Star with the Pirates, Mark was acquired by the Nationals on July 30, 2016 in exchange for left-handed pitcher Felipe Rivero and minor-league left-handed pitcher Taylor Hearn. In 2015, Mark led the Major Leagues with 51 saves and established a club record in that department. He converted 51 of his 53 save chances for an MLB-best 96.2 save percentage and was the recipient of the Trevor Hoffman National League Reliever-of-the-Year award.
He has a shark named after him from a trip taken to Southern New Zealand in which a diver tagged one of the sharks with the name “Melancon” in his honor.