Randy Johnson turned 42 years old yesterday. Today, he will take the mound for the Yankees in their series finale against the Boston Red Sox at Yankee Stadium. By nobody's standards -- yours, his, or those of his team -- is he having the kind of season he was supposed to have. Which, at 42, is the kind of thing that gets a big-league pitcher thinking about how long he wants to keep going. "When you've done the things I've done in this game, and you're used to performing at a certain level, and all of a sudden you can't perform to that same level, you start to think about it," Johnson said last week. "I'm not saying that's the case, but it's the kind of thing that makes you think." Johnson did not say specifically this could be his last season. And he did not mean to indicate that 2005 numbers that are coming in below his career's stratospheric standards would lead him to consider retirement. But he didn't rule it out, either. Reminded that he had two years left on his contract, Johnson quickly said, "Maybe." Asked if that meant he was considering quitting, Johnson said, "Well, I wouldn't call it quitting. After 17 years, I might call it retiring."