Prior to playing professionally, Pacheco attended La Cueva High School and then the University of New Mexico, where he played from 2005 to 2007. In 2005, he hit.408 with 15 home runs and 52 RBI in 52 games, earning 3rd team All-America and first-team All-Mountain West Conference. In 2005, he played with the Northwoods LeagueLa Crosse Loggers where he hit.287 with a team Leading 13 2B's. He played in 62 of the possible 64 games that summer. In 2006, he hit.351 with 11 stolen bases in 59 games with the University of New Mexico, once again earning first-team All-Mountain West Conference. He also played for the Yarmouth-Dennis Red Sox of the Cape Cod League that year, hitting.190 in 42 games and posting a 1.35 ERA in four relief appearances. In 2007, he hit.397 in 55 games, being named first-team All-West Conference for the third straight year and earning Mountain West ConferencePlayer of the Year honors. He was drafted in the ninth round of the 2007 amateur draft and began his professional career that season.
Professional career
Colorado Rockies
Pacheco split his first professional season between the Casper Rockies and Tri-City Dust Devils, hitting a combined.287 with 64 hits in 62 games. In 2008, he played for the Dust Devils and hit.280 in 54 games. He hit.323 with 13 home runs, 79 RBI and 12 stolen bases for the Asheville Tourists in 2009 and was named a South Atlantic League All-Star as well as the South Atlantic LeagueMost Valuable Player. In 2010, he played for the Modesto Nuts and Tulsa Drillers, hitting a combined.323 in 125 games, walking 60 times while striking out only 44 times. He was a California League All-Star that season. In 2011, he made his Major League debut with the Colorado Rockies on September 6 against the Arizona Diamondbacks. He went 2 for 4 with 2 RBI, although he did commit a throwing error. He played in 21 games for the Rockies that September, hitting.286 with 2 HR and 14 RBI. Pacheco cracked the Opening Day roster in 2012 as a reserve player, but after appearing in 5 games, he was optioned to Triple-A Colorado Springs. He played in 17 games with the Sky Sox, recording a hit in all but 2, hitting.433 with 3 HR and 10 RBI before returning to the Rockies on May 5. He was named the starting third baseman on May 15, replacing Chris Nelson and Jonathan Herrera. He got extended time at first base and catcher during August and September, with Nelson retaking the hot corner. Overall in 2012, he hit a rookie-leading.309 with 5 HR and 54 RBI. He finished 6th in the National League Rookie of the Year Award voting. Pacheco made the Opening Day roster in 2013 mostly playing first base along with the retiring Todd Helton. After a hot April in which he hit.339 with 6 RBI, he cooled off in May and June, receiving less playing time. On July 29, he was optioned to Colorado Springs and was replaced by Charlie Culberson. By the time of his option, he was hitting.229 with 1 HR and 17 RBI. After 18 games with the Sky Sox, he was hitting.315 with 1 HR and 6 RBI, and on August 19, he was recalled to replace back-up catcher Yorvit Torrealba, who went down with a concussion. When Torrealba returned, Pacheco stayed, and played through September with the Rockies. In 95 games with the Rockies in 2013, he hit.239 with 1 HR and 22 RBI. In the offseason, Pacheco was converted back to a full-time catcher. He played winter ball with the Toros del Este, hitting.274 in 20 games. Pacheco made the Opening Day roster in 2014 as the backup catcher to Wilin Rosario. Pacheco was designated for assignment by the Rockies on June 4, 2014, and was replaced by Michael McKenry behind the plate. In 270 games with Colorado over 4 seasons, Pacheco hit.281 with 8 HR and 98 RBI.
Arizona Diamondbacks
On June 12, 2014 Pacheco was claimed off waivers by the Arizona Diamondbacks. He was designated for assignment on June 6, 2015.
Cincinnati Reds
On January 16, 2016, Pacheco signed a minor league deal with the Cincinnati Reds organization. On June 22, 2016, Pacheco was designated for assignment to AAA, but he opted for free agency.
Atlanta Braves
On June 24, 2016, Pacheco signed a minor league contract with the Atlanta Braves. He became a free agent after the season.
