Carlos Miguel Sierra Álvarez (matrilineal name listed as Suarez in some sources)
- Bats Right, Throws Right
- Height 6' 3", Weight 195 lb.
Carlos Sierra has pitched in Cuba, Spain and the US.
Sierra debuted with Sancti Spíritus in the 2012-2013 Cuban Serie Nacional, going 1-0 with a 4.85 ERA despite allowing only 21 hits in 13 innings. In 2013-2014, he was 2-2 with four saves and a 4.09 ERA in 18 games, walking 17 in 22 innings. He was 0-1 with a 3.68 ERA in four games to open 2014-2015 then claimed Spanish citizenship as his grandfather was from Spain.
Signing with the Marlins Puerto Cruz, he dominated Spain's Division de Honor in the summer of 2015 at 11-1, 1.47. He was 4th in the league in ERA (between Mathew Erickson and Trevor Caughey), 5th in opponent average (.188, between Ramon Rosso and Zael Honora), 7th with 86 innings pitched, 8th with 85 strikeouts, first in wins (one ahead of Leslie Nacar and Honora) and tied for third with 14 games pitched. The Marlins won their third straight pennant. As he already had Spanish citizenship, it was easier for him to sign with a MLB team than someone who left Cuba illegally. Houston Astros scout Charlie Gonzalez signed him in January 2016.
The right-hander was one of two Cuban hurlers who took the Cuba-Spain-US route to pitch for the Spanish national team in the 2016 World Baseball Classic Qualifiers, alongside Rogelio Armenteros. He made his lone appearance in a loss to Colombia, relieving Antonio Noguera with a 5-0 deficit in the 5th, the bases loaded and two outs. He got Harold Ramírez on a fly to end the inning. In the 6th, he walked Dilson Herrera, retired Reynaldo Rodríguez and allowed a single to Jesús Valdez but got Adrián Sánchez to hit a double play grounder. Nacar relieved him in the 7th.
He made his US debut with the Tri-City Valley Cats (1-2, Sv, 5.53 in 12 G) then moved up to the Quad Cities River Bandits (1.80 ERA in 3 G). He began 2017 back with Quad Cities (0-1, Sv, 1.93 in 4 G), earning a quick promotion to the Buies Creek Astros (3-1, Sv, 3.24 after 21 G).