We know the Yankees want to keep their 2018 payroll below $197 million, in order to reset their luxury-tax obligations. They're currently looking at both pitchers and position players, one source said, shopping opportunistically for value, more so than need.At the moment, the Yankees' payroll commitments add up to roughly

We know the Yankees want to keep their 2018 payroll below $197 million, in order to reset their luxury-tax obligations. They're currently looking at both pitchers and position players, one source said, shopping opportunistically for value, more so than need.

At the moment, the Yankees' payroll commitments add up to roughly $162 million, according to Cot's Baseball Contracts.

By that calculation, one might conclude that general manager Brian Cashman has $35 million left to spend.

That's not accurate.

Instead, sources say the Yankees' tentative plan allows for another $15 million in spending this offseason -- unless Cashman frees up additional payroll by trading reliever Player Page for David Robertson or outfielder Jacoby Ellsbury .

Here's why: Under baseball's Collective Bargaining Agreement, the payroll calculation for the Competitive Balance Tax includes benefits, insurance and performance bonuses paid to players on the Major League roster. For the Yankees, that figure could be at least $10 million in 2018.

Moreover, the Yankees want to allocate another $10 million to spend at the non-waiver Trade Deadline and on callups during the season.

That leaves $15 million.

In this context, it's important to note that the Yankees have worked for years to gradually bring their payroll into compliance with the CBT, in anticipation of the celebrated 2018-19 free-agent class. The Yankees are wary of overcommitting now, in a way that jeopardizes their chance to reap the rewards of that restraint.

And so -- at least with the Yankees' current construction -- it's difficult to imagine them being able to afford free-agent starter Yu Darvish , who is expected to sign for more than $15 million per season. The Yankees could use some of the money they budgeted for trades and callups to sign Darvish, but that would be risky given the injury concerns that persist, to varying degrees, surrounding starters Masahiro Tanaka and Carsten Sabathia .

In effect, Darvish would represent the Yankees' free-agent splash and Trade Deadline move, all in one transaction.

The Cubs and Twins -- both of whom are pursuing Darvish, sources say -- could render the Yankees' question academic by signing the right-hander. And that outcome could suit the Yankees well, allowing them to sign a less expensive starter and a veteran complement ( Todd Frazier , Neil Walker ) for their youthful infield. Mike Moustakas remains available, too, coming off hitting a franchise-record 38 home runs last season for Kansas City.

To do something extensive -- like signing Moustakas -- would involve sending away a large contract, and Ellsbury's is a popular choice among Yankees supporters. But it's been difficult for the Yanks to move Ellsbury, given his disappointing offensive numbers and large salary.

The other issue for the Yankees as it pertains to Moustakas is that because he received a qualifying offer from the Royals and the Yankees exceeded the luxury-tax threshold in 2017, they would have to give up their second- and fifth-highest selections from the 2018 Draft as well as $1 million of their international bonus pool to sign him. So even if the third baseman decided to roll the dice and sign a one-year deal in order to test the market again next year, it's extremely unlikely that the Yanks -- who don't have an established third baseman -- would give up two Draft picks and the bonus-pool money to sign a player to a short-term contract. It's more likely they'd look for a short-term fix at third this year and make a run at Manny Machado when he is a free agent next offseason.

Consider the two-year, $6 million contract Austin Jackson recently signed with the Giants. Jackson's OPS+ was better than that of Ellsbury over the past three seasons, albeit in fewer games. If Ellsbury were a free agent now, he might receive only $3 million or $4 million per annum -- especially with other options like Jarrod Dyson , Jonathan Jay , Carlos Gomez and Cameron Maybin still available.

Instead, Ellsbury is due roughly $68 million over the next three years on a guaranteed contract. The Yankees would need to eat the vast majority of it, or swap it for another team's onerous contract, to trade Ellsbury.

Of course, there is one way it makes sense to sell low on Ellsbury: Saving $3 million or $4 million per year -- even if the Yankees must pay the rest of the contract -- can help Cashman build a World Series champion while sustaining the $197 million dream.

Jon Paul Morosi is a reporter for MLB.com and MLB Network. He has also covered baseball for FOX Sports, the Detroit Free Press and the Seattle Post-Intelligencer.