Stubbs was hitting .118 with two home runs and 5 RBIs in 24 games and had struck out 31 times in 51 at bats.
Rockies manager Walt Weiss said he believes Stubbs, who is making $5,825,000, needs to work on his rhythm and timing at the plate. Because Stubbs has five years of major league service, his consent was needed for the minor league assignment.
"It's a situation where we felt like Drew just needed to get away from the heat of the major leagues so he could go down and work on some things. He was in full agreement," Weiss said. "He was very professional about it. He understands. He wants to go down there and get right."
Barnes made the Rockies' opening-day roster last season and appeared in 132 games, batting .257 with eight homers and 27 RBIs. He was hitting .205 with five homers and 12 RBIs in 33 games for Albuquerque since being optioned April 1.
"Obviously, we know Brandon well," Weiss said. "He was with us all last year. He brings a ton of energy and the ability to play all three outfield spots."