Jiménez made his MLB debut on September 26, 2006. He came in as a relief pitcher for the Colorado Rockies during the eighth inning of an 11–4 home loss to the Los Angeles Dodgers. He allowed two hits and no runs. He would make his first MLB start on October 1 against the Chicago Cubs on the road, which was the last game of the regular season. Jiménez allowed three hits and three earned runs over a span of innings in an 8–5 loss. He didn't receive a decision for the game.