DENVER -- Once-touted left-hander Drew Pomeranz struggled with control and location once again, and he didn't make it past 4 1/3 innings -- once again. But his performance had stiff competition for the Rockies' biggest bummer of Monday night.
The offense managed a Troy Tulowitzki fourth-inning homer and nothing else as the Marlins -- who had lost four straight and hadn't scored in 37 innings before putting up two runs in the first inning against Pomeranz -- won, 3-1, before 31,913 at Coors Field.
The loss dropped the Rockies four games behind the new National League West leaders, the Dodgers, who overtook the D-backs on Monday.
Pomeranz (0-4) gave up five hits, walked four, didn't offer the Rockies (48-52) any momentum and faces an uncertain future in the rotation. But for all his struggles, he left with a two-run deficit, and relievers Manuel Corpas for 2 2/3 innings and Wilton Lopez for two innings didn't give up another run.
Since scoring a total of 17 runs in two games against the Dodgers at Coors on July 3 and 4, the Rockies have scored five or more runs just twice. Several of the games have been against top pitchers, but others -- like Monday night's -- haven't.
The Marlins are using this season to find out if right-hander Tom Koehler (2-5) is a starter or a reliever. That answer will reveal itself in the future, but all the Rockies know is they were unable to put together any kind of rally against Koehler.
"We got some hits, but we couldn't string anything together," Rockies manager Walt Weiss said. "When you score one run, you're not going to win many games.
"We have a talented offensive lineup. It's a matter of executing the game and executing at-bats. We've got to do a better job."
After scoring four runs on just five hits Sunday against the Cubs, they had eight hits off Koehler in seven innings and nine hits total on Monday -- including Tulowitzki's 17th homer, three singles by DJ LeMahieu, and a single and a double by Michael Cuddyer. Yet, combinations that added up to runs were lacking.
Three times in the first six innings, the Rockies put the leadoff runner on base. Cuddyer doubled after Tulowitzki's leadoff homer in the fourth. But none of those runners advanced beyond second base.
"Fortunately enough, I spent some time in the [Pacific Coast League], where I got to play at some higher altitude parks," Koehler said. "Still, you can't really prepare for it if you don't play there every day. But what I did learn is when you're trying to throw a breaking ball or you're trying changeups and everything, when you try to do too much with them, they just continue to spin.
"So really, just all it is about setting your sights a little bit lower than where you would normally throw them."
An offense that put three starters in the All-Star Game -- Tulowitzki, NL home run leader Carlos Gonzalez and Cuddyer -- struggling for such a period is raising questions locally.
"I know coming in here, everybody's thinking, 'Oh, the Marlins are in town,'" said Tulowitzki, whose homer came on a 3-0 pitch. "But we had a meeting before [the normal start-of-series meeting] and said these guys have good arms, some quality arms. If they put together some good swings, they can be a tough team."
The Rockies had never seen Koehler.
"We didn't put it together, and it was already the seventh inning and he was out of the game," Gonzalez said.
The Rockies will encounter another new face -- the Marlins' 20-year-old All-Star, righty Jose Fernandez -- on Tuesday night.
It was more of the same pitching from behind for Pomeranz, whose lack of production stands out on a rotation that includes solid performers in Jhoulys Chacin, Jorge De La Rosa and Tyler Chatwood, as well as the rapidly improving Juan Nicasio.
A possible replacement went down Sunday. Right-hander Armando Galarraga, obtained in a trade with the Reds last Monday, suffered a right forearm strain while batting in his debut at Triple-A Colorado Springs and had to leave that game. Righty Collin McHugh, who came in a deal with the Mets earlier this season, pitched six strong innings for Colorado Springs at Tucson on Saturday in his last start.
The big catch for the Rockies when they sent former ace Ubaldo Jimenez to the Indians, Pomeranz has made five starts since coming up from Triple-A Colorado Springs, and Monday's 4 1/3 innings matched his debut for his longest outing. He gave up five hits and walked four, but by escaping with three earned runs, he lowered his ERA by .66, to 8.10.
"We've got to have quality starts, and we know Drew is capable of doing it," Weiss said. "It's just we've got to get him right."
Pomeranz gave up three runs on three hits -- Ed Lucas' single, Giancarlo Stanton's RBI double and Marcell Ozuna's single -- in the first.
"You could just sense the kind of relief in the dugout when we put a couple up there early -- a lot of chatter, a lot of chirping, a lot more energy in the dugout," said Lucas, who opened the third with his second homer of the season.
Pomeranz walked Stanton and Ozuna before escaping the third. And Pomeranz walked two of the first three hitters in the fifth inning before departing.
"I think I've prepared pretty well for it, but it's just a matter of going out there and doing it," Pomeranz said. "It's the walks. It's obvious when you see I probably have as many walks  as innings pitched [16 2/3]. It's not a good thing."
Gonzalez doubled off Marlins reliever Chad Qualls with one out in the eighth, but Tulowitzki flied to left and Cuddyer grounded to short. Steve Cishek earned his 18th save, striking out two in a perfect ninth.
Thomas Harding is a reporter for MLB.com. Read his blog, Hardball in the Rockies, and follow him on Twitter @harding_at_mlb. This story was not subject to the approval of Major League Baseball or its clubs.