Mendez has made a combined 21 starts and three relief appearances at the three levels, going 12-3 with a 2.19 ERA. In a career-high 111 innings, he has averaged 5.8 hits, 3.3 walks and 9.2 strikeouts per nine innings. The 21-year-old was 4-1 with a 0.57 ERA in four starts and three relief appearances for Round Rock. Mendez was 4-1 with a 3.09 ERA in 10 starts for Frisco. He will be making his Major League debut.
"Mendez is really mature for his age," Rangers Minor League pitching coordinator Danny Clark said. "He really has a plus changeup, uses both curve ball and slider, his fastball is 92-93 with better command to his arm side."
Martinez is 1-3 with a 7.16 ERA in five starts and three relief appearances with the Rangers in 2016. He was 7-6 with a 3.91 ERA in 16 starts and two relief appearance for Round Rock.
Alberto has played in 25 games through two previous turns for Texas, with seven hits in 40 at-bats while playing all four infield positions. He was hitting .275 in 63 games for Round Rock.
Nicholas, a left-handed hitter, was with the Rangers from April 10-May 4, with nine hits, including two home runs, over 35 at-bats in 10 games. He played in 101 games for Round Rock, hitting .288 with 13 home runs, 58 RBIs, a .351 on-base percentage and a .458 slugging percentage.
T.R. Sullivan has covered the Rangers since 1989, and for MLB.com since 2006. Follow him on Twitter @Sullivan_Ranger and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.