With the moves, the Rockies roster sits at 39, with the one opening to be filled when the club officially signs free-agent reliever LaTroy Hawkins.
Players first signed at age 18 must be added to 40-man rosters within five seasons or they become eligible to be drafted by other organizations through the Rule 5 Draft process. Players signed at 19 years or older have to be protected within four seasons. Clubs pay $50,000 to select a player in the Major League phase of the Rule 5 Draft, slated to take place on Dec. 12. If that player doesn't stay on the 25-man roster for the full season, he must be offered back to his former team for $25,000.
In other words, an international player or high school draftee signed in 2009, assuming they were 18 or under as of June 5 of that year, must be protected. A college player taken in the 2010 Draft is in the same boat.
Matzek and Parker are both former first-round picks, with Matzek being selected 11th overall in the 2009 First-Year Player Draft and Parker 26th overall in 2010.
Matzek, 23, went 8-9 with a 3.79 ERA last year for Double-A Tulsa and walked 76 while striking out 95 in 142 1/3 innings. He made 10 relief appearances in the Arizona Fall League and was 1-1 with a 3.86 ERA.
Parker, 24, hit .288 with 23 doubles, 23 homers and 74 RBIs for Tulsa last year and was selected to the midseason and postseason Texas League All-Star teams. He hit .278 with nine doubles, four homers and 18 RBIs in the Arizona Fall League.
Aquino, 20, split last season between Class A Asheville and Class A Tri-City (short season) and posted an overall ERA of 4.34 with 26 walks and 73 strikeouts over 87 innings.
It was the first full season at the Minor League level for Aquino, who is from the Dominican Republic. He was signed by the Rockies as a non-drafted free agent on July 2, 2009, and he pitched for their Dominican Summer League team in 2010, '11 and part of '12.
Sitton, 25, made 52 relief appearances for Class A Modesto in the California League last year and was 6-5 with a 2.93 ERA. In the Fall League this year he had an 8.00 ERA in nine innings of work.
Fernandez, 23, was originally signed by the Rockies as a non-drafted free agent on Nov. 13, 2007, out of the Dominican Republic. A catcher at the time, Fernandez converted to the mound prior to the 2009 season and he sports a fastball in the upper 90s.
Last year Fernandez made 35 relief appearances for Asheville and was 2-2 with a 6.29 ERA. He struck out 14.4 batters per nine innings and had a 5-to-1 strikeout-to-walk ratio.
Herrera, 21, was originally signed by the Rockies as a non-drafted free agent on July 2, 2009, out of the Dominican Republic, and he spent last year with Ashville, where he hit .343 with 33 doubles, 16 homers, 76 RBIs and 21 stolen bases.
Herrera was named the league's Most Outstanding Major League Prospect by MLB.com and was named to the midseason and postseason All-Star teams as well as to the TOPPS Class A All-Star team.
Matthes, 26, was originally selected by Colorado in the fourth round of the 2009 First-Year Player Draft, and he split last season between Tulsa and Triple-A Colorado Springs, where he combined to hit .281 with 30 doubles, 20 homers and 63 RBIs.