The New York Yankees, winners of five in a row and eight of 10, are on a roll, climbing to within 3.5 games of a postseason spot as they head to Tampa Bay—one of the American League’s wild-card leaders—for a three-game series this weekend.

With Andy Pettitte showing signs of life on the mound, Alex Rodriguez‘s drama fueling the collective spirit of the team last Sunday night in Boston, and a much-improved offense since the return of Curtis Granderson and the acquisition of Alfonso Soriano, the Yankees might just have enough to make a real run through September and into the postseason.

Of course, it won’t be as easy as it’s looked over the last two weeks. If the Yankees do rally all the way back and qualify for October again, they’ll have to overcome two stumbling blocks: the impending disappearance of the hapless Toronto Blue Jays from their schedule and CC Sabathia’s yearlong issues on the mound.

Upon the completion of yesterday’s sweep of the Toronto Blue Jays, the Yankees moved to 12-1 on the season against the preseason American League East favorites. During those 13 games, New York has outscored Toronto by 28 runs. If you remove the Blue Jays from the ledger, the Yankees are 57-58 on the season. New York’s run differential, currently sitting at plus-two, would be a staggeringly poor minus-26.

In other words, they’ve been a below-average team when facing everyone but the 2013 Toronto Blue Jays.

With six games left on the schedule against Toronto, pencil the Yankees in for four or five more crucial victories, but the bulk of their time against each other has passed. If New York is going to continue sweeping series and winning 70 to 80 percent of its games in the midst of a big run, it’ll have to find a way to be better against the rest of baseball.

Of course, winning against the rest of baseball would be an easier task for this Yankees group if it had the CC Sabathia who arrived in the Bronx in 2009 and dominated in pinstripes. Thus far in 2013, he’s been nothing close to the pitcher who was worth a contract in excess of $161 million.

From 2009 to 2012, Sabathia pitched to a 3.22 ERA, struck out 8.2 batters per nine innings and posted a K/BB ratio of 3.34. In other words, he was a star, giving the Yankees durable, excellent pitching atop the mound.

For a team always in the mix for a postseason spot, his ability to perform better as the season wore on became a calling card for the left-hander and was something New York could bank on if wins were needed in the second half of the season.

Since debuting for the Indians in 2001, Sabathia has pitched to a 3.45-average ERA in the second half of the season, compared to 3.69 in the first half. Since arriving in New York, his second-half ERAs were 2.74, 3.29, 3.44 and 3.29.

Thus far in 2013, Sabathia has pitched to a 7.86 ERA since the All-Star break, failing to complete the seventh inning in five of his six starts. In 34.1 innings, Sabathia has allowed a whopping 63 batters to reach base.

As the Yankees try to make a run, long winning streaks and the ability to stop one-game skids from becoming two or three will be critical to catching and surpassing the teams above them in the standings.

Without the Blue Jays to beat up, the Yankees will need much better pitching from their ace.

If they don’t get it, the stumbling blocks toward a run at October could be too much to overcome.

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