Now they just about have a stranglehold on the AL West after beating the Texas Rangers twice in less than 24 hours.
Colon scattered seven hits over eight scoreless innings and the division-leading A's won 1-0 Saturday, stretching their division lead over Texas to 5 1/2 games with two weeks left in the regular season.
"I don't think it's much difference because last year we wanted to win every game, and right now we feel like we want to win every game still," said Josh Donaldson, who drew a walk in the first and scored the game's only run. "If anything, it might be a little bit different for them. ... Now they're looking up at us and trying to catch us."
Oakland overcame a five-game deficit against the Rangers in the final nine games last year, including a season-ending three-game sweep at home to clinch the division. Texas has 15 games left -- but only one against the A's in Sunday's series finale.
The A's won for the seventh time in eight games and have already clinched the key division series. They built a 9-2 lead in Friday night's opener and held on to win 9-8 after Texas had a six-run eighth.
"It's big for us to be able to pull these victories off," A's center fielder Coco Crisp said. "One was weird, the other one today was just a pitcher's duel."
Colon (16-6) struck out seven and lowered what is already his career-best ERA to 2.73. The 40-year-old right-hander became the first to reach 20 victories against Texas, his most wins in his career against any team and the most by any pitcher against Texas -- breaking what had been a tie with Bert Blyleven, Dennis Leonard and Jack Morris.
"Bartolo was just absolutely phenomenal today and didn't really give them that much of a chance," Donaldson said.
Darvish (12-9) struck out 10 over seven innings in his fourth 1-0 loss of the season. The right-hander from Japan has lost his last four starts, the last two by 1-0 scores, and is winless his last six.
Texas scored two runs or less for Darvish his last seven starts. That includes his 2-1 win at Houston on Aug. 12 when he took a no-hitter into the eighth inning.
"I can't control it. I can't do anything about it. The only thing I can do is concentrate on the batter in front of me," Darvish said through an interpreter, insisting that he is not frustrated. "As a pitcher, you can't control how many runs are scored. Am I going to go into the lineup and help the lineup? I can't."
Darvish struck out the side in the first, but Donaldson walked and scored on a two-out double by Brandon Moss into the right-field corner. Second baseman Ian Kinsler's relay throw to the plate was a bit up the line.
Colon walked one before Grant Balfour worked the ninth for his 38th save in 40 chances.
Texas has lost all five games on this homestand, and is 2-10 in September.
"It put us in second place. That's about it," manager Ron Washington said. "We've still got games left to play. We're going to continue to play."
Other than the A's last season, only two other teams have overcome deficits of five games or more with 15 or fewer games left since 1969, according to STATS. In 2007, Philadelphia had a 5 1/2-game deficit against the New York Mets with 15 games left, the same the Rangers face now. The St. Louis Cardinals were 5 1/2 games behind Houston with 11 games remaining in 2001.
Darvish had his majors-best 12th game of at least 10 strikeouts this season, and the 20th in his 58 career games. He also surpassed 250 strikeouts, becoming only the fourth pitcher to accomplish that within his first two MLB seasons. The others were Tim Lincecum, Dwight Gooden and Herb Score.
The 12:06 p.m. start was the earliest ever at Rangers Ballpark, which is in its 20th season. And it came after a 4-hour, 9-minute game Friday night that matched the fourth-longest nine-inning game in park history. That game ended at 11:16 p.m. ... The last MLB pitcher with four 1-0 losses in the same season was Orel Hershiser in 1989. ... Balfour had allowed seven runs over his previous seven games, but converted five of six saves in that span.