The Chicago Cubs were trailing by one when they put runners on first and second with one out in the seventh. It was a golden opportunity to possibly move in front of the Colorado Rockies.

Then came a strikeout and a missed sign, and it was over.

Brett Jackson belted a two-run homer but the Cubs managed just one hit in the final five innings of a 4-3 loss to the Rockies on Saturday.

Chicago had a chance to tie it in the seventh when Jackson walked and moved into scoring position on Joe Mather's one-out single. But David DeJesus struck out swinging against Rex Brothers and the inning ended when the runners broke and catcher Wilin Rosario easily threw Mather out at second.

"Coach tells you not to go anywhere and you do, that's (a sign) missed," Cubs manager Dale Sveum said. "We had the matchup we wanted with (Josh) Vitters up there against a left-handed pitcher. You don't need to be going."

Andrew Brown hit his first career homer and pinch-hitter Josh Rutledge had a two-run shot for Colorado, which has won six of seven. Carlos Torres (3-1) threw 2 1-3 scoreless innings as four Rockies relievers combined for five sparkling innings.

Colorado grabbed the lead for good when Carlos Gonzalez used his speed to beat out a potential double-play ball in the seventh inning, allowing DJ LeMahieu to come home for a 4-3 advantage.

"Pull off a couple of double plays sitting right in our laps there and they kind of changed the game around," Sveum said.

Chicago has lost five of six and seven of nine, but Jackson has been a bright spot of late.

The young outfielder connected in the Cubs' three-run fourth inning against Alex White, belting a drive to center for his second homer in two days and No. 3 for his career — all in the last week.

"I think I hit that home run 367 feet and the wall is 368," Jackson said. "But I'll certainly take it."

Jackson, who entered with a .172 batting average, went 2 for 3 with a double and a walk.

Rutledge hit for White in the fifth and drove the first pitch he saw from Brooks Raley over the wall in left, trimming the Cubs' lead to 3-2. Rutledge has been out of the starting lineup since Aug. 19 with a sore quadriceps.

"Everything he's done is impressive. We're trying to nurse him along," Tracy said.

Raley, recalled from Triple-A Iowa before the game, allowed five hits, struck out four and walked three in his fourth career start.

Brown hit a tying solo shot off Manuel Corpas in the sixth. Brown hit 24 home runs in 100 games with Triple-A Colorado Springs before the Rockies promoted him on July 17. His first home run in the majors arrived in his 26th game.

"It was a nice milestone. Hopefully it's not the last," Brown said. "It was a great feeling to come through at the time."

Corpas (0-1) was charged with two runs in 1 1-3 innings against his former team as the Cubs dropped to 5-18 in August.

Rafael Betancourt worked the ninth for his 26th save in 31 chances. He has converted nine of 10 opportunities in August.

"What we did today that we didn't do yesterday was execute late in the game to win a one-run game," manager Jim Tracy said. "We took a terrific job from Carlos Torres through all the guys to (Betancourt), their aggressiveness throwing strikes."

NOTES: Reliever Alex Hinshaw made his Cubs debut when he pitched to Gonzalez in the seventh. The Cubs claimed Hinshaw off waivers from the Padres on Aug. 19. ... Chicago optioned LHP Chris Rusin (0-1, 1.80 ERA) to Triple-A Iowa before the game. Rusin is expected to return to the majors when rosters expand in September. . Rockies SS Troy Tulowitzki (groin) and 1B Jason Giambi (viral syndrome) began rehab assignments with Double-A Tulsa on Friday. Tulowitzki went 1 for 3 with a double in five innings. Giambi went 1 for 3 with an RBI. ... Sveum said he doesn't expect the team to call up many players in September. "I don't think it'll be an overwhelming amount, but just enough to help us out in September where we can do some things roster-wise during the game and pinch hit, three to four pitchers to help out," he said.