The New York Yankees currently sit in first place in the American League East, a position they've either held or shared for 37 days of the 2014 season, and yet the storm clouds are looming large. The problem, of course, is pitching; despite rumblings about the middle infield, the team's starting rotation was always going to be its weak point. A contender can deal with a black hole of offense out of the second base position. It cannot so easily stomach a group of arms with as many question marks surrounding them as the Yankees' starting five had going into the season. The good news for the Yankees, of course, has been Masahiro Tanaka, who already has thrown 58 innings of 2.17 ERA ball (66 K, 7 BB) going into his next start on Tuesday. The bad news has been just about everything else.

The latest flashpoint for concern: former staff ace CC Sabathia, who has not pitched since an outing against the Milwaukee Brewers on May 10, in which he only lasted 5.1 innings and gave up 4 runs (only 1 earned). It was revealed on Monday that Sabathia "received a cortisone shot with stem cells Thursday as treatment for a degenerative condition in the cartilage in his right knee" from Dr. James Andrews, and that he will be out of action until the end of June. In a vacuum, that may or may not be a blessing for the Yankees. So far this season, Sabathia has managed only 46 innings pitched of 5.28 ERA baseball, getting hit much harder than he's accustomed to. Batters are slugging .528 against him this year, compared to his .382 career mark.

Oddly enough, a number of his peripheral stats have looked promising, as he's walking fewer batters (4.8 walk percentage compared to 7.2 career) and striking out more of them (23.0 whiff rate compared to 20.8 career), all while suffering through an unsustainably high home run problem (23.3 home run/fly ball percentage compared to 9.3 career). Unfortunately, all of those are consistent with hitters teeing off on a pitcher who no longer has the velocity or deception to make hitters miss, when he throws the ball for a strike.

That's where the "degenerative" part of "degenerative knee condition" could be coming into play. Sabathia had surgery on his right knee in both 2006 and 2010, and his velocity declined across the board following the 2011 season. While arm injuries -- shoulder injuries, in particular -- are the most common culprits of lost velocity, a bad knee ruining a pitcher's ability to drive with his lower body can be just as devastating. (Sabathia is a lefty, so he steps forward with his right leg, ending his delivery with most or all of his weight on it.) There's a danger in reading too much into month-to-month velocity changes, but the general trend is clear. Sabathia's "hard" pitches have declined from almost 95 mph in 2011 to barely 92 mph in 2013, while offspeed pitches (mostly changeups) have fallen from 88 mph in 2011 in 85 mph in 2013. They're even slower so far in 2014 (90 mph for hard pitches, 84 mph for offspeed) but like many pitchers, Sabathia generally builds velocity as the season goes on, so it makes little sense to judge him based solely on April and a bit of May.

That's not all bad news, of course. An 88 mph changeup is only preferable to an 85 mph changeup if that pitcher's fastball is at least three miles per hour faster, too. Sabathia has preserved a seven mph difference between his fastball and change, and a pitcher with Sabathia's command definitely can succeed in the majors with a fastball sitting 91-92, a change at 84-85 and a good slider. Sabathia has shown the ability to adapt to his new normal, and he was improving throughout April until the inflammation in his knee overwhelmed him. (The knee apparently began acting up before a disastrous May outing against the Rays, in which Sabathia didn't escape the 4th inning, and then became unbearable after the start against Milwaukee.)

The question is whether or not the knee is going to keep on getting worse, and if the velocity's going to keep on dropping -- around 88 mph, even a pitcher with great command is going to have problems keeping good hitters from smacking a fastball around the diamond. The word "degenerative" pretty much means the answer to that question is "yes."

There's also the question of whether a cortisone shot (stem cells or no stem cells) is really all that Sabathia's knee is going to need. It's good that there's no structural damage to the ligaments or the meniscus, but cortisone is not a treatment that resolves injuries; its purpose is to allow players to play through them. Whether Sabathia will need surgery in the offseason to address the cartilage issue -- whether there is, in fact, anything that can remedy the situation -- is a question that only Sabathia's doctors will be able to answer, and only after his season ends.

All of which leaves the Yankees with the old curse of the vengeful fortuneteller: "Be careful what you wish for." Tanaka has been excellent, but only Tanaka has been both excellent and healthy. Sabathia is gone until July, realistically, and it's unlikely he'll be able to perform at a substantially higher level than what Yankees fans have seen over the past 14 months or so. Michael Pineda, whose great start to the season was overshadowed by his pine tar gaffe against the Red Sox, is currently on the disabled list with an upper back injury; Ivan Nova, an inconsistent rollercoaster ride of a pitcher who is a solid No. 3 at his best, will miss the rest of the season (and likely some of the next) recovering from Tommy John surgery.

That leaves the Yankees with Tanaka; a 39-year-old Hiroki Kuroda, who has barely resembled last year's effective veteran workhorse so far (54.2 IP, 4.61 ERA); Vidal Nuno, who in a perfect world is a long man and emergency starter (34.0 IP, 5.82 ERA); and two all-hands-on-deck stopgaps in David Phelps (27.0 IP, 3.33 ERA) and Chase Whitley (4.2 IP, 0.00 ERA). There are people out there who have high hopes for Phelps to continue his success, and for Whitley to follow Phelps' lead, but I'm not among them. Phelps has been unable to crack the weak back end of the Yankees' rotation for three years, and the Yankees only began looking at Whitley -- a Troy University product who has never thrown over 100 innings in a season as a professional -- as a starter with any sort of seriousness last season, three years into his minor league career. Neither of these things are coincidental.

But there's really no other help coming for New York, not yet, anyway. Pineda should be back by mid-June, Sabathia in July, and while Nuno-Phelps-Whitley is a very dire middle and back-end of the rotation, it's not going to be the status quo for so long that the Yankees could do something truly panicky, like try to convert rookie relief sensation Dellin Betances back into a starter. (One assumes the organization learned their lesson there with Joba Chamberlain.) Unless Kuroda figures things out and Phelps or Whitley reprise Phil Hughes's 2009 out of nowhere, even a Yankees rotation with a healthy Pineda and a "healthy" Sabathia is a Yankees rotation that's in serious trouble.

If the Yankees are still hanging on in the divisional race come the trade deadline -- and given how underwhelming the AL East has been so far this year, they may still be leading it -- it won't be a question of whether someone like Mark Buehrle or Jeff Samardzija will be wearing pinstripes. It'll be a question of what it costs the Yankees to make it happen.