The Oakland Athletics' remarkable turnaround over the last three months has them atop the AL wild-card race, and the West leaders are well within reach.
The Baltimore Orioles are already enjoying the view from the top of their division.
There's plenty at stake for these two surprising contenders as this series kicks off Friday in Oakland, where the first-place Orioles look to clinch their first winning season since making their last playoff appearance in 1997.
Coming into the season, a mid-September series between Oakland (82-61) and Baltimore (81-62) seemed likely to garner about as much buzz as a sparsely attended spring training game. Instead, this three-game set has wide-ranging ramifications.
The Athletics' 56-26 record since June 11 is baseball's best, and the numbers in that stretch - 118 homers and a 3.21 ERA, both second in the majors - offer plenty of evidence for why they've been so effective.
Baltimore's rise is harder to quantify. The Orioles have a negative-20 run differential, but they've been nearly unbeatable in close games. They wrapped up a three-game sweep of fellow contender Tampa Bay on Thursday with a 3-2 victory in 14 innings, improving to 27-7 in one-run games with their 13th straight extra-inning win.
That guaranteed Baltimore would finish with at least a .500 record, but considering it's tied with the Yankees atop the East, that's not the end game for manager Buck Showalter's club.
"There's a bigger goal in mind,'' Showalter said. "That wasn't the goal from Day One this spring. Really, Day One of the offseason. It's watching other teams for years and saying, 'We want to do what they're doing. We'd like to get a chair at the dance, you know?'"
Oakland is also currently sitting in one as the top wild card and lurking three games behind West-leading Texas. It was denied a sweep of Anaheim with a 6-0 loss Thursday, but after winning the previous three games, is 4 1/2 games up on the Angels - currently third in the wild-card chase - to make the postseason cut.
Friday marks the start of Oakland's lone home series in a 20-game stretch. After this weekend, the A's play three in Detroit, three in New York and four at Texas.
"It doesn't get any easier, but I don't think there are any easy teams in the American League, to tell the truth,'' manager Bob Melvin said. "At times, you'll catch teams when they're down, but everybody we play from now until the end of the year we'll consider basically the same type of challenge and we'll have to play well to win.''
Oakland and Baltimore split six previous meetings - all at Camden Yards - and neither of Friday's starters were involved. The Orioles' Joe Saunders (2-1, 4.24 ERA) was with Arizona during those previous contests, but he'll be looking for a third straight win in the opener.
Saunders had a rocky debut with Baltimore on Aug. 29 but tossed 6 1-3 scoreless innings at Toronto on Sept. 3, then held the Yankees to two runs over 5 1-3 in Saturday's 5-4 victory.
The left-hander held Oakland to two runs over six innings in a 4-3 win for the Diamondbacks on June 10, improving to 4-0 with a 1.16 ERA in his last four starts against the A's.
Oakland center fielder Yoenis Cespedes missed that game with an injury, and Saunders may avoid him again. Cespedes left Thursday's game with a sprained left wrist and is day to day.
The A's hand the ball to Tommy Milone (12-10, 3.90), who has never faced Baltimore. Milone tied a career high with 10 strikeouts while holding Seattle to two runs over six innings in a 4-2 road win Sunday.
The left-hander, whose home ERA was 0.91 through eight starts, has a 6.75 ERA in Oakland over his last five.
With his next victory, Milone will break the Oakland record for wins by a rookie that was set by Chris Codiroli in 1983 and equaled by Joe Blanton in 2005.