(Sports Network) - Suddenly, the Diamondbacks are a team that can be beat. Arizona will try to halt its season-long losing streak tonight in the opener of a three-game series against the Colorado Rockies at Chase Field.

Arizona was swept in three games by the Chicago Cubs in the Windy City over the weekend, giving the Diamondbacks three straight losses for the first time this year. It was also the club's sixth loss in its last eight games, and Arizona's lead over Los Angeles for first place in the National League West now stands at 3 1/2 games.

The Diamondbacks dropped Sunday's finale, 6-4, as Conor Jackson tripled and drove in a pair of runs for Arizona. Miguel Montero and Eric Byrnes each doubled and scored, while Augie Ojeda and Justin Upton drove in a run apiece.

The start of game was delayed for 58 minutes due to rain, so Arizona scratched scheduled starter Randy Johnson. Edgar Gonzalez started in his place and allowed two runs on five hits in five innings. Tony Pena (0-1) took the loss after allowing two runs in 1 2/3 innings of relief.

Johnson will now start tonight for Arizona. He is 2-1 with a 5.06 earned run average this year after besting Philadelphia last Tuesday. Johnson gave up four runs on six hits, but also struck out six in six innings of work to claim the victory.

The towering left-hander, who is 14 wins shy of 300 for his career, has yet to face Colorado this year due to starting the season on the disabled list because of back surgery. He is 15-7 with five complete games and a 2.27 ERA in 24 career starts versus the Rockies, who are batting .195 against him. Johnson has fanned 222 Colorado hitters in 178 2/3 innings against the club.

Johnson will also try to extend Arizona's 2008 success against the defending NL champion Rockies. The Diamondbacks won their first five matchups with Colorado before losing to the club, 13-5, the last time they met on April 13.

Colorado has followed a three-game win streak with back-to-back losses, including Sunday's 6-1 setback in San Diego. Garrett Atkins went 1-for-4 and scored the only run for the Rockies.

Greg Reynolds (0-1), who was called up prior to the game for his first big league start, absorbed the loss after he was touched for four runs on six hits in 5 2/3 innings.

Turning to a pitching prospect didn't help Colorado end its losing ways, and tonight the club will rest its hopes on an ace that is still searching for his first win of 2008.

Jeff Francis won 17 games for the Rockies last year, but is 0-3 with a 5.27 ERA through seven starts this season. That includes two losses in two starts versus Arizona on April 5 and 11, and the left-hander has a 9.53 ERA against the Diamondbacks this year.

Francis has been unable to keep Arizona in the ballpark this season, allowing six home runs against them, including two each to both Upton and Chris Young. He is 7-4 with a 4.25 ERA lifetime against Arizona in 16 starts.

Francis got a no-decision in his last start, yielding three runs on six hits and a season-high five walks to St. Louis on Wednesday. He left the game trailing 3-0, but the Rockies plated four runs in the eighth inning to claim a victory.