These NL West rivals both try to get on track in the opener of a three-game set at Coors Field on Friday night.After entering the year as a heavy favorite to repeat as division champion, Los Angeles (31-30) has dropped six of eight to fall 8 1/2 games behind first-place San Francisco. The Dodgers, hitting .204 during their struggles, were limited to a season-low two hits in Wednesday's 2-1 defeat to the Chicago White Sox."We're just not that good," manager Don Mattingly said. "We're just not getting it done. Losing at home, away, whatever."Matt Kemp is mired in a 4-for-38 slump, and Adrian Gonzalez and Hanley Ramirez are a combined 2 for 28 in four games this month. Ramirez owns a .253 average after hitting a career-best .345 last year."I don't know what to say," Ramirez told MLB's official website. "We're not doing anything right now, so we've got to start playing better. Everybody is unhappy with the way we're playing."The Dodgers won't get any sympathy from the Rockies (28-31), who have lost seven straight for their longest skid since dropping nine in a row from Sept. 15-23, 2012. Colorado was outscored 32-17 during a three-game sweep against Arizona after Thursday's 12-7 defeat."We come to play every single day," said Troy Tulowitzki, who went 2 for 4 with his team-leading 16th homer. "It's just not happening right now."The Rockies surrendered a combined 16 runs in the eighth and ninth innings in the last two losses."I don't know," manager Walt Weiss replied when asked if this is rock bottom. "We have a game tomorrow. We'll try to win a game tomorrow."Colorado will try to bounce back against Hyun-jin Ryu (6-2, 3.09 ERA), who has won three consecutive starts. The left-hander allowed a season-high 10 hits Saturday but managed to limit the damage, yielding two runs over six innings in a 12-2 win over Pittsburgh."He bends but doesn't break," Mattingly said. "Guys get in scoring position, they act a little differently and get anxious. He seems to be able to take advantage of that."Contrary to Mattingly's remarks, Ryu couldn't wriggle his way out of trouble in a 6-1 loss to Colorado on April 27. He was tagged for six runs over five-plus innings, dropping to 1-2 with a 5.40 ERA in the series.While he's struggled against the Rockies, Ryu has been nearly untouchable on the road, going 4-0 with a major league-leading 0.56 ERA and 32 strikeouts in as many innings.Colorado counters with top prospect Eddie Butler, who will be called up from Double-A Tulsa to make his major league debut. The 23-year-old right-hander went 3-0 with a 0.74 ERA in his last four minor league starts."If I go out there and pitch six innings and have us in the ball game, that's going to be a great day," he said. "I just want to get out here and help the guys win."A strong showing from Butler could go a long way for a Rockies rotation that's posted a 7.35 ERA during its skid."He's got a great arm. He's a great competitor. He seems unflappable. I think he'll take the mound on Friday night and expect to do well. That's more than half the battle," Weiss said. "He's been very dominant at times over the last couple of seasons. We knew he was a big leaguer, it was just a matter of when. And the time is now."