- Sport: baseball
- Team: Baltimore Orioles
- Position: catcher
- Nationality: Venezuela

- Birth date: 1981-11-29 (27 years)
- Place of birth: Maracaibo, Venezuela, Venezuela
Guillermo Antonio Quiroz was born on November 29, 1981 in Maracaibo, Venezuela. He is a Major League Baseball catcher, currently a backup catcher for the Baltimore Orioles.
Minor Leagues
Guillermo was signed by the Toronto Blue Jays as a non-drafted free agent in 1998, before his 17th birthday, with a $1.5 million signing bonus.
He progressed through Toronto's farm system as the team's number-one catching prospect. Indeed,, Baseball America rated him as the Blue Jays' third best prospect in their 2004 pre-season rankings, and the 35th best prospect in all of baseball.
1999 - Medicine Hat Blue Jays, in the Pioneer League
2000 - Queens Kings, in the New York-Penn League, then promoted to the Hagerstown Suns of the South Atlantic League.
2001 - Charleston AlleyCats in the South Atlantic League.
2002 - Dunedin Blue Jays in the Florida State League and then was promoted to the Syracuse SkyChiefs in the International League.
2003 - New Haven Ravens in the Eastern League
2004 - Syracuse SkyChiefs in the International League.
2005 - Dunedin Blue Jays, in the Florida State League, and then the Syracuse SkyChiefs.
2006 - (for the Seattle Mariners) San Antonio Missions in the Texas League, and then the Tacoma Rainiers in the Pacific Coast League
2007 - (Texas Rangers) Oklahoma RedHawks in the Pacific Coast League.
Injuries slowed his progress- he missed the end of the 2003 season with a collapsed lung, and had a broken hand in May 2004.
In 2006, the Blue Jays signed two more catchers, and placed Guillermo on waivers. He was picked up by the Seattle Mariners, and sent into their minor league system.
Guillermo was signed by the Texas Rangers on December 28, 2006. He spent most of the 2007 season with the Triple-A Oklahoma RedHawks until a September call-up to the majors. At the end of the 2007 season, the Rangers designated him for assignment, but he refused to go and became a free agent.
On December 3, 2007, he signed a one-year major league contract with the Baltimore Orioles. He is the backup catcher for Ramon Hernandez.
Guillermo's problem is that although he has excellent defensive skills, he can't hit.

Minor Leagues
Guillermo was signed by the Toronto Blue Jays as a non-drafted free agent in 1998, before his 17th birthday, with a $1.5 million signing bonus.
He progressed through Toronto's farm system as the team's number-one catching prospect. Indeed,, Baseball America rated him as the Blue Jays' third best prospect in their 2004 pre-season rankings, and the 35th best prospect in all of baseball.
1999 - Medicine Hat Blue Jays, in the Pioneer League
2000 - Queens Kings, in the New York-Penn League, then promoted to the Hagerstown Suns of the South Atlantic League.
2001 - Charleston AlleyCats in the South Atlantic League.
2002 - Dunedin Blue Jays in the Florida State League and then was promoted to the Syracuse SkyChiefs in the International League.
2003 - New Haven Ravens in the Eastern League
2004 - Syracuse SkyChiefs in the International League.
2005 - Dunedin Blue Jays, in the Florida State League, and then the Syracuse SkyChiefs.
2006 - (for the Seattle Mariners) San Antonio Missions in the Texas League, and then the Tacoma Rainiers in the Pacific Coast League
2007 - (Texas Rangers) Oklahoma RedHawks in the Pacific Coast League.
Injuries slowed his progress- he missed the end of the 2003 season with a collapsed lung, and had a broken hand in May 2004.
In 2006, the Blue Jays signed two more catchers, and placed Guillermo on waivers. He was picked up by the Seattle Mariners, and sent into their minor league system.
Guillermo was signed by the Texas Rangers on December 28, 2006. He spent most of the 2007 season with the Triple-A Oklahoma RedHawks until a September call-up to the majors. At the end of the 2007 season, the Rangers designated him for assignment, but he refused to go and became a free agent.
On December 3, 2007, he signed a one-year major league contract with the Baltimore Orioles. He is the backup catcher for Ramon Hernandez.
Guillermo's problem is that although he has excellent defensive skills, he can't hit.

Team history
- Baltimore Orioles (2008 - present day)
- Texas Rangers (2007 - 2007)
- Seattle Mariners (2006 - 2006)
- Toronto Blue Jays (2004 - 2005)
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