The latest evidence came Tuesday, in one of the more impressive wins the Yankees have manufactured this season. Andy Pettitte made it that way, blanking Tampa Bay for eight innings and poking a few holes in its momentum. And the end result was a 5-0 win that was as necessary for New York's own self-esteem as it was for its actual standing.
Rays, meet the Yankees. They can be mighty, too.
"We came to play," catcher Jose Molina said. "And we're going to continue to come and play and show everybody we're for real."
Nearly everything they accomplished Tuesday hinged on Pettitte. Coming off one of his worst starts of the year -- he had allowed six runs in 4 2/3 innings to the Red Sox on Thursday -- Pettitte retired the first two Rays he saw on two pitches. Then he mowed through the rest of baseball's best team, allowing only one batter to reach second base through the first six innings.
In the seventh, he found trouble, putting runners on the corners with two outs and putting manager Joe Girardi on the edge of his seat. But then Derek Jeter -- still plenty mighty himself -- stabbed a grounder deep in the hole, spun and made an impressive jumping throw to second.
"And Robbie Cano's there waiting for it," Girardi said. "It's a huge out for us."
Jeter, naturally, had only one thought on his mind.
"Just turn and make sure you don't throw it into right field," he said.
Pettitte threw one more perfect inning, and Edwar Ramirez pitched a scoreless ninth. Then, as they have so many times over the past decade against the Rays, the Yankees gathered in the infield to shake hands and celebrate a win.
Only this one was different. This time, the inherent edge seemed to lie with the Rays.
"They're ahead of us," Pettitte said. "We knew we needed to beat them."
And so they did, scoring all the necessary runs when Jeter doubled home Molina and Cano with two outs in the third. That seemed significant given Scott Kazmir's start -- he struck out seven batters over the first three innings and featured a "doggone good fastball," according to Pettitte -- and remained significant until game's end.
The Yankees (48-42) scored three more runs in the eighth on Melky Cabrera's homer, Bobby Abreu's double and Cano's single, ensuring a win that was already secure.
In the context of the season, of course, the Yankees accomplished little Tuesday. They remain 7 1/2 games back of the Rays -- as much as those figures matter with nearly three months to play -- and they remain underdogs to win a playoff berth. But given what Tampa Bay accomplished last week against Boston at Tropicana Field -- a sweep -- and the relative ease with which it has won all season, there was a certain bit of relief that surrounded this win.
Yes, the Rays (55-34) are good. Perhaps even better than the Yankees.
But that doesn't mean the Yankees can't beat them.
"We know the importance of the game as well as they do," Girardi said. "We know we have to play better on a consistent basis if we want to play October baseball."
Pettitte hesitated to call it a "big" series, though he didn't shy away from this week's significance. His greater agenda, however, was erasing the memories from his last start against Boston, and his eight scoreless innings achieved that end quite well. Relying almost exclusively on fastballs and cutters, Pettitte allowed four hits and walked none. He struck out five, and most importantly, he earned his 10th win.
"Just another start," he said, and perhaps he was right. But not everyone agreed.
"He was outstanding tonight," Girardi said. "It's a big win for us."
And perhaps the first of many.
"We're just starting right now," Molina said.
The luxury of a two-game series -- or perhaps the curse -- is that there's a whole lot of importance riding on a short span of play. Should the Yankees win again Wednesday, they'll certainly have sent a not-so-subtle message to the Rays, and indeed to the rest of the league. Should they lose, then they'll give back everything they've gained.
But they'll enter Wednesday's game with something novel: the hard evidence that yes, these upstart, lovable, even mighty Rays can be beaten.
Which, in turn, means that they can be beaten again.
"I think about just playing good baseball," Girardi said, minutes after watching precisely that. "Because you've got to worry about yourself and what you do."
Anthony DiComo is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.