A series win is still within reach, however. The A's, who haven't lost any of their last 11 sets, remain one game behind the Mariners in the race for the second American League Wild Card spot with Seattle's extra-innings loss to the Angels on Friday night.
Back-to-back doubles from Matt Chapman and Jed Lowrie in the seventh accounted for their lone run Friday, though Oakland had ample opportunity for more.
The A's specialty has been coming through the eighth, and the makings of yet another come-from-behind victory -- Oakland had 17 of them in its previous 27 games -- came to life when it loaded the bases for a third time, only for Chapman, facing Rockies reliever Scott Oberg, to strike out looking.
"I think everybody knows that we were in that ballgame, and unfortunately, we just couldn't get those big hits," Chapman said. "I don't think we're going to dwell on this one too much."
The A's, who averaged 8.5 runs in their previous six games, came up with nine hits but left 13 on base, including five in the first two innings, and finished 1-for-10 with runners in scoring position.
"Our best at-bats again came later in the game," A's manager Bob Melvin said. "We were just one big at-bat short tonight. Give them some credit. They made some big pitches when they had to, but it felt kind of the same, that someone was going to come up with a big hit. We just didn't come up with it today. But, similar to the other games, we put ourselves in a position to."
Left-hander Sean Manaea, who picked up his first Major League hit with a second-inning single, was left with little room for error and subsequently took his first loss since May 30 as he was bested by Rockies southpaw Kyle Freeland. Manaea allowed three runs over five innings with a season-high nine hits allowed, two of which were bunts that helped the Rockies jump ahead to a 1-0 lead in the second.
Manaea was tagged for two more runs in the fifth, which featured a solo homer from Nolan Arenado. The Rockies' Gold Glove Award-winning third baseman, who played high school ball with Chapman, did his part on defense, as well, generating an inning-ending double play in the fifth to squash Oakland's bases-loaded threat.
Chapman also showed off on both sides of the ball. The A's third baseman reached base three times, singling and doubling on the heels of a two-triple night on Thursday.
"When I saw him out there, he told me I looked good," Chapman said. "I'm happy to be here and it's fun to play against him. I don't know what I can tell him that he hasn't already heard, but it's just cool to be out there. Unfortunately, he got the better of us tonight, but [we have] two more games."
MOMENTS THAT MATTERED After Manaea was lifted at 74 pitches, the A's got two scoreless innings from right-hander J.B. Wendelken. His work, which featured three strikeouts, helped the club get through a night when at least four relievers -- including the club's big three of Blake Treinen, Lou Trivino and Jeurys Familia -- were unavailable.
"He picked us up big time," Chapman said. "Our bullpen has been carrying a big load for us as of late, and they've been doing a great job. That's a big outing from him. You can't live and die by one game. You got to think big picture. We can't burn everybody every game, so for him to pick us up like that is huge."
SOUND SMART The A's lost for the first time this season on the road when allowing three or fewer runs.
HE SAID IT "He's starting to get a little more confident. With that kind of stuff, he should be. He's got a plus-fastball, used his breaking ball better today, has his changeup. We wanted to get him here for a reason because we felt like he could be a nice arm for us." -- Melvin, on Wendelken
UP NEXT Lefty Brett Anderson, who suited up for the Rockies in 2014, will take the mound for the A's in Saturday's 5:10 p.m. PT matchup at Coors Field. Anderson is 2-0 with a 3.14 ERA in three starts since his return from the disabled list. Colorado will counter with right-hander Antonio Senzatela (3-3, 5.55 ERA).
Jane Lee has covered the A's for MLB.com since 2010.