The Cardinals' No. 2 prospect gave up a run on two hits over six innings Saturday night as Springfield shut down Northwest Arkansas, 5-1.
Martinez (2-2) arrived from Palm Beach about a month ago and has yet to allow more than two earned runs in a Texas League start. Saturday's effort was the second straight outing in which he's gone six innings and yielded just one run.
"He's got a good arm, a nice and easy delivery. The ball really jumps out of his hand," Springfield manager Mike Shildt said. "He's really been able to throw strikes with the fastball, keep the ball down, and he's been effective with both his four- and two-seamer. With that velocity he has, it's a real good pitch."
After giving up a solo homer to Carlo Testa with two outs in the second, Martinez allowed only three more baserunners on an error, a walk and a single. He ended up issuing two free passes while striking out three.
Martinez, MLB.com's No. 23 overall prospect, was good in the Florida State League, but he's been a little bit better in transitioning to Double-A. He was 2-2 with a 3.00 ERA and 34 strikeouts over 33 innings at Palm Beach.
The 19-year-old right-hander has a 2.30 ERA and 21 strikeouts against six walks over 27 1/3 innings in six starts with Springfield.
Shildt said he wasn't too surprised one of the Cardinals' most prized arms has adapted as quickly as he has to his new surroundings.
"We're optimistic by nature here and he has ability," he added. "When a guy has ability, we're just trying to get him to understand how to use it. [Pitching coach Bryan Eversgerd] has got a good plan with him, the catchers are on the same plan, so we're just letting him pitch and letting his talent play."
So far, it has.
In 13 starts across the two levels, the native of the Dominican Republic is 4-4 with a 2.69 ERA, 55 strikeouts and only 16 walks over 60 1/3 innings. He's also surrendered just one home run.
It's a departure from last season, when Martinez posted a 2.33 ERA in eight starts at Class A Quad Cities, then made the jump to the FSL, where he found things more difficult. In 10 starts with Palm Beach last summer, he had a 5.28 ERA and walked 30 while fanning 48 in 46 innings.
Shildt cited Martinez's maturity for his more successful adjustment this year.
"The one thing that's been impressive is he's been really aggressive, competed well," he said. "He's done the little things we like to see -- held his runners, fielded his position, just gone about things in a positive way."
Oscar Taveras went 3-for-3 in support of Martinez, giving the No. 3 Cardinals prospect a .395 average in nine games this month. Chris Swauger chipped in a two-run homer.