Ramírez began with the Colorado Springs Sky Sox of the triple-A Pacific Coast League. After throwing a scoreless inning for Colorado Springs, he was called up by the Rockies on April 12 when Mike DeJean was placed on the disabled list. He made his debut on April 14, pitching two scoreless innings in a 10–8 loss to the Philadelphia Phillies. Five days later, he singled against Chan Ho Park in his first major league at bat in a 13–4 loss to the San Diego Padres. On April 25, he pitched scoreless innings and got his first major league win in a 7–6 victory over the Phillies. Ramírez began his career with scoreless innings in 11 games, which set a Rockies record for longest streak by a reliever to begin a career. It was the longest streak by a reliever to start a career since Jeremy Fikac threw 16 scoreless innings to start his career in 2001. Ramírez's streak ended on May 15, when he allowed three runs in of an inning and got his first career loss against the Los Angeles Dodgers, who won 5–4. On August 15, he set a career high with four innings pitched in the longest game in Rockies history, an 18-inning game against the Arizona Diamondbacks. He gave up a run in the 18th and suffered a loss in the 2–1 defeat. He had a 2.88 ERA in his first 47 games, but he posted a 5.09 ERA over his final 14 games, raising his season ERA to 3.46. On September 30, in his final game of the season, he pitched scoreless innings and got the win in a 14-inning, 11–9 victory over the Chicago Cubs. Ramírez finished the season with a 4–3 record, a 3.46 ERA, 61 strikeouts, and innings pitched in 61 games. His 61 games were the third-most by a Rockies' rookie pitcher, behind Steve Reed (64 in 1993) and Javier López (75 in 2003).