There is a 10-day period in which designated players can be traded, released or accept an assignment to the Minors.
Added to the Kansas City roster along with Guthrie were left-handed pitchers Mike Montgomery, John Lamb, Chris Dwyer, Donnie Joseph and Justin Marks and right-hander J.C. Gutierrez, all elevated from the Triple-A Omaha roster.
The moves came at mid-afternoon on Tuesday, well ahead of the 10:59 p.m. CT deadline to set rosters and protect players from the Rule 5 Draft of Minor Leaguers on Dec. 6 at Winter Meetings in Nashville, Tenn.
Players first signed at age 18 must be added to 40-man rosters within five years or they become eligible to be drafted by other organizations through the Rule 5 process. Players signed at 19 years old are to be protected within four years.
Clubs pay $50,000 to select a player in the Rule 5 Draft. 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.
The Royals hope that the highly-regarded Montgomery will find his groove after two subpar seasons in the Minors. He was a combined 5-12 in 27 starts last season for Omaha and Double-A Northwest Arkansas. In 2011, he went 5-11 for Omaha.
Montgomery is rated the Royals' sixth-best prospect on MLB.com's Top 20 list. Lamb, despite missing most of the 2011-12 seasons after undergoing Tommy John surgery on June 3, 2011, is ranked ninth among Royals prospects. He made six starts this year in Rookie and Class A ball.
Joseph was acquired from the Reds for closer Jonathan Broxton and, after the trade, was 1-0 with a 4.15 ERA in 11 games for Omaha. He struck out 19 and walked 13 in 17 1/3 innings. Counting his time with Triple-A Louisville, Joseph was 9-3 with a 2.33 ERA in 55 relief outings. He's the Royals' 10th-ranked prospect.
Dwyer, rated No. 12 among KC prospects, split time between Northwest Arkansas and Omaha and was 8-12 with a 5.89 ERA in 26 games, all but one of them starts. He had 104 strikeouts and 68 walks in 136 innings.
Marks, who came from the A's with Mazzaro two years ago in a trade for outfielder David DeJesus, had a strong Arizona Fall League season. He was 5-1 with a 2.59 ERA in seven starts. Last summer, Marks pitched for three teams, mostly Northwest Arkansas, and was combined 3-6 with a 4.50 ERA in 20 games (19 starts).
Gutierrez, a former Major Leaguer with the Astros and D-backs, has seven saves, a 1-1 record and a 1.50 ERA in 13 games for Leones del Caracas in the Venezuelan Winter League. He missed most of 2011 with a shoulder ailment and pitched in 19 games this year in the Royals' system.
Of the players designated for assignment, Pena has the longest tenure with the Royals -- four seasons and 264 games since he was claimed off waivers from the Braves in 2008. A backup catcher, the switch-hitter had a .251 average for Kansas City.
Mazzaro, a right-hander obtained as a starter from the A's, made six starts this year, but was used primarily in relief. He was 4-3 with a 5.73 ERA in 18 games for the Royals.
Verdugo, a left-hander, came to KC with pitcher Jonathan Sanchez last winter in the trade for outfielder Melky Cabrera. For Omaha, Verdugo posted a 12-4 record and a 3.75 ERA in 27 games (24 starts) and made one start for the Royals, but was chased in the second inning by the Mariners.
Clint Robinson had some big seasons in the Minors -- he had 23 homers, 100 RBIs and a .326 mark for Omaha in 2011 -- but as a designated hitter and first baseman was blocked in KC by Billy Butler and Eric Hosmer. This year, he was called up during Interleague Play and went 0-for-4 as a pinch-hitter. For Omaha, he slipped to 13 homers, 67 RBIs and .292.
Derrick Robinson hit .268 and swiped 23 bases this year for Omaha. He also was named left fielder on the 2012 Minor League Rawlings Gold Glove Award team.
Moore was claimed on waivers from the Mariners on July 7 and played 35 games for Omaha with a .296 average and 22 RBIs. Called up by KC in September, he got in four games and went 2-for-11.
Volstad figured in the Royals' rotation possibilities after being claimed from the Cubs, but was dropped to make room for Guthrie. Volstad was 3-12 with a 6.31 ERA in 21 starts for the Cubs this season.