The Chicago Cubs fell 10-5 to the Colorado Rockies on Tuesday in the opener of a three-game series at Colorado that was shortened to seven innings because of rain.

How it happened:: The Rockies jumped on Cubs starter Chris Rusin with six runs over 3 2/3 innings. The Cubs actually led 3-0 in the first inning, getting a leadoff home run from Dave Sappelt, an RBI double from Welington Castillo and another run on a Rockies error. Starlin Castro added a home run in the third inning. The Rockies scored three times in the fourth inning but the big blow was a three-run home run from Matt McBride in the fifth inning.

What it means: It was the attack of the former Cubs as Tyler Colvin had a two-run triple among his two hits, while DJ LeMahieu had an RBI double among his three hits, while also scoring two runs. Both were sent to the Rockies in December in the deal that landed the Cubs third baseman Ian Stewart, as well as right-hander Casey Weathers. Stewart has been out since June 12 with a wrist injury

Outside the box: Cubs relievers Rafael Dolis and Manny Corpas gave up a combined four runs on eight hits over 2 1/3 innings. It was some rare struggles from a Cubs bullpen that had actually settled down of late. The relievers had pitched to a 2.98 ERA over the last 16 games. Before Tuesday the bullpen had also struck out 64 batters over the last 63 1/3 innings, good for 9.1 strikeouts per nine innings.

Off beat: In a battle of clubs hoping to avoid 100-loss seasons, the Rockies moved closer to their goal. Both teams came into the game with 59-94 records, which meant they each needed four victories to guarantee no more than 99 defeats. By losing, the Cubs are alone with the 29th worst record in baseball, ahead of only the Houston Astros, who have already wrapped up the worst record in baseball this season.

Up next: The Cubs will send right-hander Jason Berken (0-1, 1.80 ERA) to the mound Wednesday against Colorado in the middle game of the three-game series. The Rockies will counter with left-hander Drew Pomeranz (1-9, 5.30) in the 7:40 CST start from Coors Field.