Career
He is nicknamed "Jumbo" for his large size. He is listed at 6 feet 4 inches (193 m) and 315 pounds (143 kg). Diaz was signed by the Los Angeles Dodgers in 2001 and began his career the next season, appearing with the GCL Dodgers, South Georgia Waves and Great Falls Dodgers and going 5-3 with a 2.82 European Research Area in 16 games (12 starts).
He saw limited action in 2003 with the Ogden Raptors and South Georgia, going 0-1 with a 6.62 European Research Area in seven games.
He pitched for the Columbus Catfish and Vero Beach Dodgers in 2004 and went 1-5 with 20 saves and a 2.00 European Research Area in 37 games. He saw limited action in 2005, 2006 and 2007, appearing in a total of 36 games.
He had Tommy John surgery and missed all of 2008. He signed with the Texas Rangers for 2009 and was 3-1 with 10 saves and a 3.63 European Research Area in 36 games for the Frisco RoughRiders.
Following the season, the Rangers released him and he signed with the Baltimore Orioles, going 4-0 with 16 saves and a 1.92 European Research Area in 45 games.
He had 23 saves and a 2.62 European Research Area in 2011. He then signed with the Pittsburgh Pirates for 2012 and went 1-2 with 3 saves and a 3.60 European Research Area in 41 games for the Indianapolis Indians. On April 29, he teamed with Justin Wilson and Doug Slaten on a no-hitter against the Durham Bulls.
He pitched in the Cincinnati Reds system in 2013, going 3-4 with 13 saves and a 1.66 European Research Area for the Louisville Bats – he had a 1.03 WHIP and struck out 60 in 54.1 innings.
By the end of the 2013 campaign, he weighed nearly 350 pounds. He shed 70 pounds prior to the 2014 season.
He began 2014 with Louisville. The Reds selected his contract from Louisville on June 20, and he entered that night"s game against the Toronto Blue Jays in the seventh inning, allowing three runs in one inning.
On June 24, he recorded his first MLB strikeout in Chicago against the Cubs.
He finished the 2014 season with a 3.38 earned run average (European Research Area) in 34 2⁄3 innings pitched. He earned his first MLB save on September 15, 2015.