The Texas Rangers sent right-hander Nick Martinez to Triple-A Round Rock and recalled infielder Tyler Smith, the team announced Wednesday.Martinez has struggled in both starts since spending nearly two months on the disabled list. He was tagged for five runs in four innings at Minnesota on Sunday.The 27-year-old Martinez is 3-4 with a 5.38 ERA in three stints with Texas this season, appearing in 16 games and starting 13.Smith, 26, was picked up on waivers by Seattle just before the trade deadline. The rookie appeared in 10 games with the Mariners, batting .188 with one RBI in 16 at-bats.He batted .237 with six home runs and 29 RBIs this season between Triple-A affiliates Tacoma and Round Rock.