Here's the stakes.
For the Yankees, starting ace CC Sabathia: A win gives them 3 out of 4 in this series, and a 2 1/2-game lead, reduces their Magic Number to clinch the American League Eastern Division Championship to 8, and gives them the inside track to their 47th 1st-place finish, including (should they win it) 19 AL East titles. While a loss would not be catastrophic, it would be problematic, but they would still, almost certainly, win the AL's Wild Card, and while they've never won a Pennant as the Wild Card winner, other teams in each League have. Once you're in the postseason, anything can happen.
For the Rays, starting ace David Price: A win gives them a split of this series, and leaves them just a half-game out. They are already all but assured of at least the Wild Card, but a schedule that includes 3 games at home to Seattle, 3 games at home to Baltimore, and 4 games at Kansas City, as opposed to the Yankees' remaining sked of a pair of home-and-home 3-game series with Boston, bookending 3 in Toronto, gives the Rays a bit of an advantage. The Red Sox have already won 84 games, and the Blue Jays are over .500 at the moment; the Rays' opponents have lost 93, 91 and 89 respectively, and we can't count on help from them.
In other words, the Yankees WANT to win this game, but the Rays HAVE to. As I said before the series began, a split would be acceptable for the Yankees. We have clinched at least that, but last night's 7-2 Rays win (A.J. Burnett wasn't very good again) means that a sweep can't be done, but 3 of 4 still can.
Bottom line: Yanks win tonight, and both teams then go 1 game over .500 the rest of the way -- Yanks 5-4, Rays 6-4 (1 game above 5-5), and it ends Yankees 98-64, Rays 96-66, Yankees win Division; Rays win tonight, and both teams then go 1 game over .500 the rest of the way, and it ends with each team at 97-67, and the Rays win the Division via the first tiebreaker, head-to-head competition.
Of course, if the Yankees take 2 out of 3 in each remaining series, that reduces their Magic Number to 4 no matter what the Rays do, meaning that even if the Rays win tonight, they'd still have to at least split the rest of their games to win the East. If the Yankees win tonight, and then take 2 out of 3 in each remaining series, that reduces the Magic Number to 2 regardless of the Rays' performance, meaning they'd have to win 9 of those last 10. Even for the Rays, against the Mariners, Orioles and Royals, that's a tall order.
Granted, the Rays aren't facing the 2001 Mariners, 1983 Orioles and 1985 Royals. But neither are the Yankees facing 2 series against the 2007 Red Sox and 1 against the 1993 Blue Jays.
It's not often that we see an ace-vs.-ace matchup on a Thursday night. Rarer still is seeing it in a race between the top 2 teams in a Division -- in this case, the teams with the 2 best records in all of baseball.
Bring it on, Rays. Bring it, CC. Come on, Bronx Bombers, give your ace the support he needs. Close it out, Mariano.
Let's put these children to bed.