DETROIT -- Once again, Dontrelle Willis gave the Tigers a chance to win. All he could do in defeat is tip his cap to Todd Helton.

The offense behind him -- or lack of it -- left others scratching their heads.

"We've got a good ballclub, but we've got to get our offense going," manager Jim Leyland said after Helton's second go-ahead hit in as many days, this one an RBI single in a two-run seventh that sent Colorado past Detroit in a 3-1 decision Sunday at Comerica Park.

The Tigers' second straight defeat earned them their first home series loss in Interleague Play since dropping two of three to the Brewers on June 12-14, 2007. Detroit entered this series with a 42-12 Interleague record since '06, which stood atop the Majors.

But the Interleague stretch is over for a few weeks. What has to concern the Tigers going forward is an offense that managed eight runs for the series and scored more than four runs only once over Detroit's past six games since a 33-run onslaught over three games against the A's here last weekend.

The starting pitching continues to keep the Tigers in games, and Willis backed up the notion that he can give Detroit a chance to win when he takes the mound every five games. It's now up to the offense to build a lead.

It wasn't the same dominance that Willis (1-1) built over his 6 1/3 innings of one-hit ball Tuesday against Texas, but it would have been unfair to expect that. What had to be encouraging for Tigers officials was the way he responded when he didn't have his best stuff.

Willis struggled at times to find the outside corner, leading to four walks over his 6 2/3 innings. And unlike the previous couple outings, the Rockies showed a willingness to swing at the first pitch rather than allow Willis to get ahead.

Only one of those walks, however, came around to score. None of those first pitches put in play, meanwhile, resulted in base hits. And none of the rallies caused the kind of reaction from Willis that would've gotten him off the game and led to the big innings he suffered last year.

"I thought he pitched very well," Leyland said. "He did a great job changing speeds."

One of those big outs came against Helton early. Willis started the third inning by striking out Clint Barmes and Ian Stewart, but after Dexter Fowler poked a ball inside the third-base line for a two-out double, Willis walked Troy Tulowitzki on four pitches to extend the inning. A first-pitch ball to Helton and a double steal, putting runners at second and third, brought pitching coach Rick Knapp out of the dugout for a meeting at the mound.

Willis continued to work Helton outside with fastballs, spotting three of them on the corner. The last, a 92 mph heater, drew a called third strike to end the threat.

"I felt like I threw the ball well," Willis said. "I fell behind some guys."

Helton didn't have to wait long for redemption. After Willis stranded a runner in the fourth and retired the first two batters of the fifth, Fowler walked his way back on base, and Tulowitzki waited on an outside pitch to knock a ground ball through the right side. Willis tried to pitch Helton outside, but he left a fastball far enough up for Helton to turn and pull it to the right-field fence for an RBI double, ending Willis' streak of 11 scoreless innings -- dating back to Willis' first start a week and a half ago at Minnesota.

Once Helton came back up with two outs and Stewart on second in the seventh inning, Willis tried to get him to bite back outside. Once he didn't, Willis left him a pitch just far enough in for him to reach, grounding a ball up the middle. The ball went just out of reach of second baseman Ramon Santiago for the decisive RBI.

"Hats off to him," Willis said of Helton, who was 1-for-9 off Willis in his National League days. "That's Todd Helton. I've faced that guy a bunch of times."

Willis still finished with a quality start, his first such outings back-to-back since Sept. 20-25, 2007. Helton and Rockies starter Jason Hammel ensured he didn't get the win.

Detroit's lone RBI came on Dane Sardinha's second hit of the year, an RBI blooper into center that scored Magglio Ordonez after two walks and a Brandon Inge single had loaded the bases with one out. Hammel (1-3) escaped anything worse with a double play from Josh Anderson, and he went on to retire 11 of 12 batters before allowing a pair of singles in the sixth.

Anderson batted leadoff Sunday, with Curtis Granderson hitting fifth, and Ramon Santiago hit second in place of Placido Polanco. Nonetheless, the top third of the Tigers' order struggled for the second straight day, going 0-for-11 with a walk and five strikeouts after Saturday's 0-for-12 woes.

"Everybody worries so much about who's hitting behind [Miguel] Cabrera," Leyland said. "More important, who's hitting in front of him?"