NEW YORK -- When Masahiro Tanaka takes the mound Saturday afternoon against the Minnesota Twins, it will mark the Yankees' 54th game of the 2014 season, exactly one-third of the way to the finish line.

An arbitrary milepost, to be sure, but by no means a small sample size. By now, most of the regulars in their lineup are closing in on 200 at-bats. Two of their starting pitchers -- the two who have remained healthy since Opening Day -- are at or near 70 innings pitched, on track to throw a solid 200 innings by the end of the season. So it is certainly not too early to draw some conclusions about individual performances thus far.

At the same time, 54 games is by no means representative of what a full season might bring, any more than judging a 75-year-old man by his first 25 years would constitute a fair and complete biography.

Still, one thing we can say with certainty about what we’ve seen of the 2014 New York Yankees is that no one can be fully certain of exactly who, or what, they are. Or what they will be.

Are they the team that just finished taking two of three from the defending National League champion St. Louis Cardinals, at Busch Stadium, the third-toughest ballpark in baseball for a visiting team to win in this season? (By contrast, visitors have a 50-50 shot of winning at Yankee Stadium, where the home team is 11-11 so far.)

Or are they the team that lost two of three to the Houston Astros in the first series of the season, or the one that dropped both games to the Seattle Mariners at home last month?

Are they the team that shut out the Mets in consecutive games at Citi Field on May 14 and 15? Or the one that got blown out, allowing 21 runs in two games, to the same team in the same week at Yankee Stadium?

The answer to all of the above is yes.

On certain nights, the Yankees have looked very, very good. And on other nights, they have looked so bad it made you want to cover your eyes.

Even in Wednesday night’s 7-4 win over the Cardinals, the Yankees' defense was at times so atrocious as to be embarrassing. And in the same game, the offense looked overpowering for two innings and underwhelming for the other seven.

Make no mistake, this is a Jekyll and HorseHyde team so far, capable of looking like a serious contender some nights and like a ridiculous pretender on others.

Just take a look at the pattern of the first third of their season: One five-game winning streak in mid-April, and a whole lot of win one/lose one, win two/ lose three, win three/give back two more.

So far, in addition to that five-game span in which they took two from the Red Sox, two from the Cubs and one from the Tampa Bay Rays between April 12 and 17, the Yankees have had one four-game winning streak and one four-game losing streak. Two three-game winning streaks and one three-game losing streak. Four occasions in which they have won back-to-back games -- and six occasions in which they lost back-to-back games.

Every time it seems as if they are about to go on a tear, they slip back toward mediocrity. When they left to begin their just concluded nine-game road trip, the Yankees were three games over .500 (23-20), having just been beaten at home by the Pittsburgh Pirates.

They return four games over .500 after going 5-4 on the road, a rather remarkable accomplishment considering five of those games were started by pitchers who were thrust into the rotation due to injuries, and one of those losses was suffered by Tanaka, who hadn’t lost in nearly two years.

Before the season, I had predicted 92 wins for this club. Right now, if they win the first two games against the Twins, they’ll be on pace for 90.

Will that be enough to get them to October? Maybe, because suddenly the entire AL East appears to be just slightly better than mediocre.

The question is, will the Yankees be able to maintain this level of super mediocrity for another 108 games? Will they improve upon it? Or, like last year’s team, which started out even better than this one but gradually wound down, grinding on to a dreary 87-win, Octoberless finish.

Want to hear something disturbing? Last year’s Yankees, cobbled together with retreads like Vernon Wells, Lyle Overbay and Kevin Youkilis when Derek Jeter, Alex Rodriguez, Mark Teixeira and Curtis Granderson went down with injuries, went 16-10 in April.

This year’s Yankees, benefiting from an offseason investment of more than $400 million in Tanaka, Jacoby Ellsbury, Brian McCann and Carlos Beltran, went 15-11.

Last year’s Yankees followed that fine April with an almost-as-good May, and after 54 games sat eight games over .500 at 31-23.

Even giving the Yankees the first two games against Minnesota, they can’t hope to match that. The best they can be at the close of business Saturday is 30-24.

Not bad, you say? Well, this team was supposed to be better, much better than last year’s. So far, it hasn’t happened. Can anyone be sure that it will?

The very unlikelihood of how well the Yankees pitched over the just-completed stretch is what actually makes it seem unlikely.

You can practically guarantee the hitting will get better. Ellsbury, who had three hits and three RBIs on Wednesday night, is not a .268 hitter. Neither will McCann stay at .225, nor will he have an OPS of .657; .800 is more like it. Let’s take Jeter at his word that his bat will come around and assume that what Teixeira says is true, that his wrist just needed a few days of rest.

No one need make excuses for Brett Gardner or Yangervis Solarte or even Ichiro Suzuki, who has performed admirably in what must surely be a demeaning part-time role. Brian Roberts has been better than anyone might have expected. And let’s hope the positive reports on Beltran translate to a productive return to the lineup.

But the real question is, how long can the Yankees continue to rely on a rotation that includes Vidal Nuno, David Phelps and Chase Whitley? None of them are bad pitchers, and all have performed well in emergency duty. Any one of the three would be just fine as a No. 5 starter on any club. But can the Yankees really get away with all three of them as integral parts of their rotation?

Chances are Michael Pineda is headed back by mid-June, and that will help. But there is still no timetable for CC Sabathia, who was suffering through a miserable season even before he went down with a knee injury. Ivan Nova is lost until next season after Tommy John surgery.

By GM Brian Cashman’s own admission, there is no one down in Triple-A ready to make the jump, and even after the June 5 first-year player draft -- yet another arbitrary date before which few teams are inclined to make any trades -- top-flight, big league-ready starting pitchers are not easy to come by, especially for what the Yankees are in position to offer.

And without some outside help for the rotation, it’s tough to imagine this team getting a whole lot better than it is now.

True, 54 games is still a relatively truncated sample, and there are still more than 100 games to play. There is plenty of time for hitters to heat up, pitchers to find their groove and for rosters to change drastically.

Through the first one-third of the 2014 season, the Yankees have been puzzling, and at times, pretty good.

But history tells us that “pretty good" rarely cuts it in the AL East, and never in October.

It’s still way too early to panic.

And it's way too late to say it’s too early to have some serious misgivings about how this Yankees season will ultimately turn out.