Colorado @ Arizona preview

Last Meeting ( Jul 22, 2011 ) Colorado 8, Arizona 4

THE STORY: The Colorado Rockies have scored 29 runs over the last four games and will try to keep their second-half surge going Saturday night in the second of their three-game series at Arizona. The Diamondbacks have taken a step backwards offensively since the All-Star break; they averaged 4.52 runs before and only 3.29 since. The Rockies have won three of four and opened their nine-game road trip against NL West squads with an 8-4 win Friday. Arizona, now four games behind division-leading San Francisco, has lost three of four and is 4-4 on their long homestand. Arizona leads the season series 6-3.

TV: 8:10 p.m. ET, ROOT, FSAZ

PITCHING MATCHUP: Rockies RH Jason Hammel (5-9, 4.36) vs. Diamondbacks RH Josh Collmenter (5-5, 2.65).

Hammel has dropped three of his last four decisions, losing to the Braves on Monday. He gave up six runs, but two were unearned, in five innings of work against Atlanta. Hammel's numbers are better on the road, where his ERA is 3.40 and the opposition is .249 against him. He's made six career starts against the Diamondbacks, going 3-2 with a 2.95 ERA. He lost a 2-1 decision to Arizona on May 5, with both runs unearned. Collmenter had gone six starts without a win until stopping the skid with eight shutout innings against the Brewers on Monday. He's thrown 14 consecutive scoreless innings, remarkably all against the hit-happy Brewers. Righthanders are hitting only .163 against him and he's struck out 34 and walked only four. Collmenter is 0-1 with a 2.84 ERA in his career against the Rockies; he lost his only start against Colorado earlier this season, allowing five runs in 4 1/3 innings.

ABOUT THE DIAMONDBACKS (53-47): With Stephen Drew out with a broken ankle and ligament damage, the shortstop duty is expected to fall on Willie Bloomquist, with Cody Ransom standing by after being recalled from Triple-A Reno. Bloomquist is 4-for-13 in the last three games and has hit safely in 11 of 12. Ransom, 35, was hitting .331 with 26 homers and 89 RBIs, which led the Pacific Coast League. Sam Demel has struggled the last three times out, allowing four runs and six hits in 2 1/3 innings. He allowed the Rockies to score two important insurance runs Friday.

ABOUT THE ROCKIES (48-52): Dexter Fowler appears to be the likely substitute for Carlos Gonzalez at the top of the order. He hit leadoff Friday and went 3-for-5 with a double and a triple. Fowler is 10-for-28 with three doubles and three triples since being recalled from the minors July 15. Mark Ellis has hit safely in five straight games (9-for-24) and is batting .324 since being acquired from the A’s. Reliever Rex Brothers has allowed only one run and has struck out 20 in his last 16 appearances. Rafael Betancourt has retired eight of his last nine outs on strikeouts.

FINAL PITCH: Micah Owings (3-0, 2.76 ERA) will start for Arizona in the series finale Sunday. The righthander has not started since he was with Cincinnati in 2009.