Martinez, who spent much of the 2013 season in the Majors and who finished the year a key member of the Cardinals' playoff roster, recently joined the Aguilas Cibaenas, one of six teams in the Dominican Winter League. Martinez, 22, lives in the Dominican Republic during the offseason.
Cardinals general manager John Mozeliak said that Martinez asked for the organization's permission to participate in a portion of the Dominican Winter League season. The Cards gave him their blessing, though they are monitoring his pitch counts and workload.
"He felt like he really wanted to get back to work," Mozeliak said. "I think we're encouraged with where he is at. He was involved in a throwing program the last couple of weeks and ramped himself up."
In his winter league debut on Saturday, Martinez allowed an unearned run on two hits in two innings. He struck out two.
Though Martinez did not miss time due to injury in 2013, a changed role meant that he did not log as many innings as initially expected. He spent about half the season pitching out of the Major League bullpen. His season also started a bit later than usual after visa issues delayed his arrival to Spring Training.
Martinez logged 120 2/3 total innings last season. Of those, 79 2/3 came in 16 Minor League starts, 28 1/3 came with the Cardinals during the regular season and another 12 2/3 were pitched in October. Altogether, it was a modest increase over the 104 1/3 innings Martinez pitched the year before.
The Cardinals plan to have Martinez compete for a starting job this spring. Cracking that rotation, however, will be a tall task, given the number of more experienced returning starters -- Adam Wainwright, Jaime Garcia, Lance Lynn, Shelby Miller, Michael Wacha and Joe Kelly -- also looking for a rotation fit.
If Martinez does not start the season in the Cardinals' rotation, he could either slide back into the bullpen or return to Triple-A to start.
Martinez is the second member of the Cardinals' 40-man roster to play winter ball this offseason. Recently signed right-hander Angel Castro is teammates with Martinez on the Aguilas club. Castro, who is 4-3 with a 1.29 ERA in eight Dominican starts, projects to begin the 2014 season in the Triple-A Memphis rotation.
There could be another Cardinals big league player logging playing time in winter ball before the offseason is over, too. Mozeliak acknowledged this week that the organization is considering having backup catcher Tony Cruz play in January.
With Yadier Molina taking the bulk of playing time behind the plate, Cruz accrued only 123 at-bats last season. He will remain the team's backup catcher next season.